A math problem needs to be solved with equations!

Solution: Let the single-digit number of these two digits be x; The ten digits are 2x, according to the title.

10×2x+x)-36=10x+2x

21x-36=12x

9x=36x=4

So 2x=8

A: This two-digit number is 84

Solution: If the single digit is x, then the ten digit is 2x

This two-digit number can be expressed as: 10*2x+x

After exchanging the numbers, the resulting two-digit number is expressed as: 10*x+2xAccording to the title, there are:

10*2x+x-36=10*x+2x

21x-36=12x

9x=36x=4

2x=4×2=8

A: This two-digit number is 84

If the single digit is x, then the ten digit is 2x

2x*10+x=10x+2x+36

21x-12x=36

x=42x=2*4=8

So it turned out that the number was 84

Let the two-digit number be ten digits x and the single digit y

Then x=2y, (10x+y)-(10y+x)=36x=2y, x-y=4

We get x=8 and y=4

The two-digit number is 84

Let the ten digits be x and the single digit be y

y=2x10y+x-10x-y=36

9y-9x=36

y-x=4x=4

y=8 is 84 for two digits

Let the single digit number be x and the ten digit number be 2x

2x*10+x-(x*10+2x)=36

x=42x=8

A two-digit number, the ten-digit number is twice the one-digit number, and the two-digit number obtained after the two numbers are reversed is 36 smaller than the original number, find the two-digit number.

Solution: Let the digit on the original two-digit number be x, then the ten-digit number is 2x, and the two-digit number can be expressed as.

10 2x+x, the ten-digit number and the single-digit number are interchanged, and the resulting two-digit number can be expressed as 10x+2x, according to the title:

10×2x+x-（10x+2x）=36

Solution: x=4

So 2x=8

So the original two-digit number was 84.

Answer: Slightly.

Assuming that the single digit is x, then the ten digit is 2x, then the two digits are equal to x+2x*10=21x, and after the single digit is ten, it is equal to 2x+x*10=12x, then 12x+36=21x

9x=36x=4

Therefore, this two-digit number is 84

Let this number be (10x+y), which is known as: 10x+y-(10y+x)=36 to get x-y=4

and x=2y to get y=4

So the original 2-digit number is 84

If the single digit is x, then the ten digit is 2x

Title by: 10 2x x 36 10 x 2x

The two-digit number x=4 is 84

If the unit digit is x, then the ten digit is 2xx10 and the number: 21x, and the swap is: 12x

So: 21x-12x=36 rule; x=4

So: number; 84

1. Solution: There are x people who arrange the finishing first, and the question is obtained: x 60 + 2 (x + 15) 60 = 1 multiply 60 on both sides at the same time to obtain: x + 2 (x + 15) = 60

Solution: x=10

1 24 + 1 30) x + 1 40 (x-8) = 1, multiply both sides by 120 at the same time to obtain: (5 + 4) x + 3 (x-8) = 120

Solution: x=12

Answer: A total of 12 hours of pumping from start to finish 2. Question: It takes 12 days for A to complete a job alone, and it takes 6 days for B to do this work, and now A has done 3 days, and the remaining workload is completed by A and B together, how many days will it take to complete this work?

Solution: Let it take x days to complete, from the question: 3 12 + x 12 + x 6 = 1 solution: x = 3

1.Let x people work first, (x+15) 2 1 60=1-x 60, get x = 35 people 2Suppose a total of x hours to draw (1 24 + 1 40) 6 + (1 24 + 1 30 + 1 40) (x-6) = 1, x = 12 hours 3

For a project, it takes 12 hours for A to do it alone, 12 hours for B to do it alone, and 6 hours for C to do it alone, and now A does it for 3 hours first, and B and C for the rest, how many hours does it take? It takes x hours 3 12 + x 12 + x 6 = 1Get x = 3 hours.

1).One person does 1 60 in one hour, and the original x person does 3x (1 60) in 3 hours = x person does 15x2 (1 60) = 1 2 in 2 hours. (x/20)+(1/2)=1。

Multiply by 20, x+10=20, x=A ergonomics 1 24, B 1 30, C 1 40. A total of x hours. (x/24)+(x/30)+[x-6)/40]=1。

Multiply by 120, 5x+4x+3x-18=120, 12x=138, x=69 6=hour). 3).Separate house A in December, B in June.

A did it for 3 months first, and B only entered the market, how long did B do it? (3/12)+(x/12)+(x/6)=，x=3

1.Let it take x hours 1 20*4 (1 20 1 12)x=1 solution to get x=62If it is assigned to person A x person, it will be transferred to person B (20-x) 27 x=2*[19 (20-x)].

The solution is x=17, that is, 17 people A and 3 people B 3Let B's speed x B take 5 6 hours 5 6x=5*(3 2 5 6).

The solution is x=14km h, and the first question is that A works 1 20 per hour, B works 1 12 per hour, and the left side of the second question is the number of workers after A increases the number of workers, and the right side is twice the number of workers after B increases the number of workers, and the third question on the left is the speed of the bicycle * time, and the right side is the speed of walking * time.

(1) Analysis: If we know that the sum of the solution of the equation 2x+2a=x+k about x is 6, then substitute 6 into x, that is, x=6 to obtain.

2*6+2a=6+k

k=6+2a

2) Same as above: Substitute a-1 into x, that is, x=a-1 to get 3*(a-1)+2a=2

3a-3+2a=2

5a = 5a = 1 choose a

(1)2x+2a=x+k

x+2a=k

k=2a+6

2) Substitute a-1 into the equation.

3（a-1）+2a=2

3a-3+2a=2

5a=5, so a=1 choose a

1.Set the original price of this schoolbag x yuan.

80%x—60=20

Solve x=100

A: The original price of this schoolbag is 100 yuan.

2.If the original price of commodity A is x yuan, and the original price of commodity B is y, then x+y=100

x(1-10%)+y(1+5%)=100(1+2%), x=20

y=80A: The original unit price of product A is 20, and the original unit price of product B is 80

3.The original price of the product is $x.

The solution is x=280

A: The original price of the product is 280 yuan.

4 The principal amount deposited in the bank is $x.

5%×3x×（1—20%）=720

Solution x=6000

A: The principal amount deposited in the bank is 6,000 yuan.

Set the balloon to be x km above the ground.

Then 27-6x=12x=

Set the balloon to be x km above the ground.

6x=27-12

x=(27-12) 6=km.

Solution: Set the fast train to catch up with the slow train after driving for x hours.

60x－40x＝40×30/60

20x＝20

x 1 at this time the slow car is running together:

40 (30 60 1) 40 km).

Solution: Let x hours meet x+40x=300,x=3;，x=；x=40x+300，x=15；

x=40*, x=16, full car traveled 660 km.

Hour 2(300-60*1 4) (60+40)+1 4=hour-hour.

4.(300 + 40 * 1 2) (60-40) = 16 hours (16 + 1 2) * 40 = 660 km.

(1) 2 times 6 + 4 times 4 + 8 times 4 = 60 (yuan).

2) 2 times 6 + 4 times 4 + 8 (x-10) = 44 x = 13

3) Set water use x cubic meters in April. 2 times 6 + 4 (x-6) + 2 times 6 + 4 times 4 + 8 (20-x-10) = 64 x = 8 20-8 = 12 Answer: 8 cubic meters of water in April and 12 cubic meters in May.

(1) 2 * 6 + 4 * 4 + (14-10) * 8 = 60 (yuan) (2) If 10 cubic meters of water is used, the water fee is 2 * 6 + 4 * 4 = 28 (yuan), 44-28 = 16 (yuan), 16 8 = 2 cubic meters, 10 + 2 = 12 cubic meters.

3) Set x cubic meters of water used in April, (20-x) cubic meters of water used in May, and because there is more water used in May than in April, x 10

6＜x≤10,2*6+4（x-6)+8（20-x-10)+28=64

The solution is x=8x 6, 2x+28+8(20-x-10)=64, and the solution is x=22 3

If it doesn't fit the topic, give it away.

Therefore, the household used 8 cubic meters of water in April and 20-8=12 cubic meters in May.

1 14 cubic meters is divided into 3 parts, 6 cubic meters, 7-10 cubic meters, and 11-14 cubic meters.

2 6 + 4 4 + 8 4 = 60 yuan.

2 2 6 + 4 4 + 8 (x-10) = 44 yuan = > 28 + (10-x) = 44 because all 10 cubic meters are charged 28 yuan.

The solution is x=12 (tons).

3 If x tons of water are used in April, then y tons of water will be used in May, because y is larger than x, so x<10x+y=20

2 6+4 (x-6)+ 28+(y-10) 8=64 solves the above equation to obtain x=8 y=12

That is, 8 cubic meters of water will be used in April and 3 cubic meters of water will be used in May.

2.Let one set be x and the other set y

x(1+20%)=168

y(1-20%)=168

Find x and yx=140

y=210 then (168-140)+(168-210)= -14 lost 14 yuan.

1. Set the purchase price to a yuan ton, and the discount number is x 7a (1 + 50%) + 3a (1 + 50%) x = 10a (1 + 50%) 82% (a set but not squire) x =

2. Set the purchase price of profit x yuan, the purchase price of loss y yuan, (1+20%)x=168 (1-20%)y=168 x=140 y=210

x+y=350 168+168=336 So it's still a loss, a difference of 14 yuan.