The practical problems of the second year of junior high school math problems are not equal to the o

1200x---800 is greater than or equal to 800 times x greater than or equal to so 7% off.

The set price is x, so the inequality is as follows. x multiplied by greater than or equal to 760 x greater than or equal to 6400 so the minimum price is 6400 yuan.

Let's buy x pens.,So the inequality is as follows:2 times times x less than or equal to 21 x less than or equal to so you can buy up to 5 books.。

Set the guy to the right x. So the inequality is as follows: 4 times x ---25 ---x) times 1 is greater than or equal to 85x=22 So the guy has to be right at least 22.

Hehe.. It's finally done!

1.(1200*x 10-800) 800=5% x 10 because, for example, if you get a 20% discount, you will multiply it by 80%, that is, 8 10==3x

After doing it, I found that someone had already answered below, but since it was done, I still submitted it.

1 1200x--800 800+800 5% set x discount.

2 Set price to x

3 only)4 4x+(25--x) 85 Set correct x channels.

x≥20

1 The question is wrong is a maximum of 7% off.

B brand clothing y=

A brand clothing x = 2y + 4 < = 48, y< = 22 (2y + 4) * 25 + 32 * y>1740

50y+32*y>1740-100=164082y>1640

y>20

22>=y>20

y=22,x=48

y=21,x=46

The easiest way to say that "the number of clothing from brand A is 4 more than the number of clothes from brand B is twice as many as the number of clothes from brand B" is to set B to x

Details: If the number of brand B clothing purchased by the boss is x, then the number of A is 2x+4 pieces "A brand clothing can be purchased up to 48 pieces" (omitted) 2x+4 48

x 22 and "the profit that the boss can get is not less than 1,740 yuan, the profit of brand A clothing is 25 yuan, and the profit of selling a piece of brand B clothing is 32 yuan" (omitted).

2x+4）×25＋x×32≥1740

Solve x 20 (process below).

This boss has 3 options:

44 pieces of brand A and 20 pieces of brand B were purchased;

46 pieces of brand A and 21 pieces of brand B were purchased;

48 pieces of brand A and 22 pieces of brand B were purchased.

Equation solving process) (2x+4) 25 x 32 174050x+100+32x 1740

82x≥1640

x≥20

Set the number of B brand clothing to be purchased x pcs.

0＜2x+4≤48｛1｝ 25（2x+4）+32x≥1740｛2｝ ｛1｝0＜x≤22 ｛2｝x≥20 20≤x≤22 a 44 b 20 a46 b 21 a48 b22

Solution: The number of B brand clothing purchased is x, and the number of A brand clothing purchased is (2x+4).

then {2x+4 48.}

25(2x+4)+32x≥1740

Solve 20 x 22

x is an integer, and x is taken as 20, 21, 22

2x+4 for 44, 46, 48 (4 points).

Answer: There are 44 pieces of A brand and 20 pieces of B brand; 46 pieces of A brand A and 21 pieces of B brand; There are 48 pieces of A brand A and 22 pieces of B brand

44, 46, 48 pieces of clothing of type A were purchased, and 20, 21, and 22 pieces of type B were purchased.

Solution: There are a total of x students. Then there are:

0 solution: 0 is an integer: then there is x and the maximum value is 55That is, the maximum number of students in this class is 55.

The least common multiple is 28

So 28 2 = 14, 28 4 7, 28 7 = 4, and 28-14-7-4 = 3<6

The common multiple of 56 is

So 56 2 = 28, 56 4 14, 56 7 = 8 and 56-28-14-8 = 6, which is not on topic and is discarded, so there are a maximum of 28 students in this class.

It's not the same as other people's answers, you choose, forget to take it, I don't know whose it is).

The divisible by 4,7 should be a multiple of 28 set to 28x28x-14x-7x-4x<6

x < 2, while x is at least 1

So x = 1,28 people.

Solution: There is a maximum of x students in this class.

1-1/2-1/4-1/7）x<6

3/28x<6

x<56

I have always had a habit of doing questions, and I hope it will be helpful to my classmates.

First of all, find the information and problems in the stem, and only by clarifying the goal can you solve the problem.

Half of the question stems, one quarter, one in seven, and less than 6 people are the key to information and problem solving, and the question is how many students are "in total", and the total here is in stark contrast to the "leftover", which can be solved here.

In math, it's 1, which is 100%. Therefore, if the rest is compared to x, it is x=1- 1 2 - 1 4 - 1 7, so x=3 28

There are less than 6 people left, that is to say, the remaining people account for 3 28 in the class, and there is a classmate above who is counted one by one, to see if it is an integer, in fact, there is no need to count each here, the eyesight can see it, the meaning of the numerator and the denominator here he did not figure out, the numerator means the rest of the people, and the denominator is the overall person, so they can all be the same zoom in, and 12345 is a multiple of 3 on a 3, so it can only be 3 people, and the total number is 28, If this question is changed to the remaining 6 people, the numerator is doubled, and the denominator is also doubled, which is 56. So, mathematics is a thing of thinking and logic, if you like it, you will gain something, I hope you can be inspired by talking so much! Thank you o(o

Seek the best pro.

There are x number of students.

x-（x/2+x/4+x/7）＜6

3x/28＜6

x 56 has a maximum of 55 students.

Set up x people in this class. x-x 2-x 4-x 7<=6,x<=56, take the multiple interval of the least common multiple of 2, 4, 7 as the answer, then it is 28-56Up to 56.

There are x people in total.

x-1/2x-1/4x-1/7x<6

3/28x<6

x<56

So x max 55

Set the total number of x people, x-( x 56 so a maximum of 55 people.

D solution: a, the set of solutions of the given inequality group is -2 x 2, then a, b is a positive and a negative, let a 0, then b 0, the solution is x 1a, x 1b, the original inequality group has no solution, and there is no solution after changing all the signs of the two numbers, so it is wrong and does not meet the meaning of the topic;

b. The set of solutions given for the group of inequalities is -2 x 2, then a, b have the same sign, let a 0, then b 0, the solution gets x 1a, x 1b, and the solution set is positive; If the same numbers are negative, the solution set can be obtained, and all are negative; Therefore, it is wrong and does not conform to the topic;

c. The reason is the same as above, so it is wrong and does not conform to the topic;

d. The set of solutions of the given inequality group is -2 x 2, then a, b is a positive and a negative, let a 0, then b 0, the solution is x 1a, x 1b, the original inequality group has a solution, it may be -2 x 2, and the same is true after changing all the symbols of the two numbers, so it is correct and in line with the topic

So choose d hey, hey, I've done it.

Available equations:

Available: x=4

So: if: x<4 then choose A.

If x>4 then choose B.

If x=4 then A and B are the same.

Solution: There are x outstanding students at the municipal level in the school. Then:

240 + 240 * x 2)-240 * (x + 1) * 60% = 96-24x = 24 (4-x), if 4-x>0, that is: x<4, then choose B travel agency, if 4-x=0, that is: x=4, then choose anyone, if 4-x<0, that is:

x>4, then choose Carapace Travel Agency

The solution set of 9(x-3)>x+5-2a is x>-3, find a9x-27>x+5-2a

8x> staring at Niansui 32-2a

Dissolve x=-3 substitution.

24=32-2a

a=28 because x>-3, so a>28

2；（2a-b)x+a-5b>0

b-2a)x0

x>b/a=24/57

Namely. x>24/57

1) The total output value of new home appliances is x units.

Total high-level investment y=200+

Total profit y2=

When x=900.

y2=-20

When producing 900 units, the loss was 200,000 yuan.

y2>0

0x>1000

So when x > 1000 is profitable, when x < 1000 is a loss, and the bigger x is, the more profitable.

Solution: Let the price of apples be X yuan kg

50-30-3*3<3x②

Solve x <

The number in between x > can be used as the price of apples.

Let Apple** be $x.

3 3 3x 50 30 solution.

Set $x per kilogram of apples.

Then: 30+2 3+

30+3×3+3x＞50

Just solve it again.

6+ is less than 20

9+3x is greater than 20

x is greater than x less than.

Take the middle ...