Math problems, kneel and beg! chasing 100 .

x+y 3=x+z 9 gives z=3y

x+y 3=y-z 6=y-y 2=y 2 gives x=y 6x+y+z=5, i.e., y 6+y+y 3=5

25y 6=5, y=6 5

Therefore, it is x=1 5

y=6/5z=18/5

From x+y 3=x+z 9, z=3y

Substituting x+y+z=5 gives x+4y=5

y=6x is obtained from x+y 3=y-z 6

Substituting x+4y=5 gives x=

Substituting the formula gives y= z=

x+y 3=x+z 9 to get z=3y, x+y 3=y-z 6 to get x-y=-z 6-z 9; Bring in z=3y, get y=6x; Then bring in x+y+z=5;x=1 5; And then we get y=6 5, z=18 5.

From x+y 3=x+z 9, we can know 3y=z, and x+y 3=x+z 9=y-z 6, we can know the relationship between x, y, z, and then set a parameter, x+y+z=5 and it will be connected.

From x+y 3=x+z 9, z=3y

Substituting x+y+z=5 gives x+4y=5

y=6x is obtained from x+y 3=y-z 6

Substituting x+4y=5 gives x=

Substituting the formula gives y= z=

ok???

Each student has 1 bottle of mineral water per day in spring, autumn and winter, and 2 bottles per day in summer. One student buys a total of 180 bottles of mineral water in spring, autumn and winter; Buy 120 bottles of mineral water in the summer. In a year, a student buys a total of 300 bottles of mineral water.

That is, a student spends a total of yuan throughout the year.

After purchasing a water dispenser, the number of barrels of purified water required for each shift in a year is: 4 barrels per day in spring and autumn, then a total of (4 120) 320 barrels are needed for 120 days, and 5 barrels per day in summer, a total of 60 5 = 300 barrels. In winter, 1 barrel per day, a total of 60 barrels, a total of pure water (320 + 300 + 60) = 680 barrels throughout the year.

Therefore, the cost of purchasing mineral water is 680 6 = 4080 yuan. The cost of using electricity is 240 10 yuan).Therefore, the total cost of each class of students in Changbo throughout the year:

4080 + 600 + 150 = 4830 (yuan).

The savings of one student are 450 - = RMB. All students save a total of $100.

The first one was clearly wrong.

2): 1<1-a<1

1<1-2a<1

1-a<2a-1

(1): Class size: 8 (8 24-7 24) = 192 students.

2) Set a basket of akg, according to the idea: (3a+12) 5a=3 4, solution: a=16kg, so total: 16*8+12=140kg

3) Total number of books: (11 + 7 + 4) (1-1 5-1 4) = 198 books (4) After setting a, according to the title: (8 + a) (40 + a) = 1 9, solution:

a=-4, so the question is wrong! It should be 4 years ago, Wang Qiang's age was 1/9 of his father's!

5) Let there be a+15, a, according to the title: (a+15)*2 5+a=69, solution: a=45, so there is a ball! If you don't understand, I'll tell me more details, I wish you progress in your studies!

1.altogether = 8 (1 3-7 24) = 192 people 2Altogether = 5 (1-3 7) = basket.

Each basket = 12 (kg.)

Altogether = kilograms.

3.Total = (11 + 4 + 7) (1-1 5-1 4) = 40 Ben 4After X years, Wang Qiang's age is 1/9 of his father's

9(8+x)=40+x

72+9x=40+x

8x=32x=44 years later, Wang Qiang's age is 1/9 of his father's

5.Set the second box x and the first box x + 15.

x+15)*2/5+x=69

2x/5+6+x=69

7x/5=63

x = 45 60 in the first box, 45 in the second box.

1.Set up a class of x people. 7x 24+8=x 3, the solution is 24*8 192.

2.Let the total number of kilograms x. (3x 7-12) 3=(4x 7) 5, 140

3.Featuring x books. x 5 + 4 + x 4 + 7 + 11 = x, the solution is 404Theoretically, if we let x years, we get (8+x)=(40+x) 9, but the solution is -4, which is not very clear.

5.Set a total of x balls. (x-69)*5 3 69-(x-69)*2 3+15, the solution is 105.

1.Let the class size x, then 7 24x+8=9 24x-8, and get x=1922Semantics don't make sense.

3.Let the total be x, then 1 5x+4+1 4x+7+11=xThis gives x=404After x years, then 8+x=(40+x)*1 9, and x=(is there any error).

5.Let the number of balls in the second box be x, then (x+15)*2 5+x=69, that is, the second box has (how can it be inexhaustible).

When the class is finished at the meeting, I don't know if you want to use the equation solution or the elementary school method.