Xinhua bookstore sells 45 science and technology books, 89 comic books, 240 comic books and how many science and technology books?

Xinhua bookstore sells 45 science and technology books, 89 comic books, 240 comic books and how many science and technology books?

240 △ 89 × 45, = 270 × 45, = 216 (copies); answer: 216 science and technology books

Story books are a quarter more than science and technology books. How many times are story books, and how many times are science and technology books

Story books are 1 + 1 / 4 = 5 / 4 times of science and technology books,
The ratio of science book and story book is 1: (1 + 1 / 4) = 1:5 / 4 = 4:5
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Given that x = 2 is the solution of the equation 4x + 5K = 2, find the solution of the equation 2-k (2k-1) = - KX about X

Substituting x = 2 into 4x + 5K = 2K = - 6 / 5
2 + 6/5 X ( -17/5) =6/5 x
x= -26/15

The problem of simple system of linear inequalities of one variable
20 more

1、2X+3＞0
-3X+5＞0
2、2X＜-1
X+2＞0
3、5X+6＜3X
8-7X＞4-5X
4、2（1+X）＞3（X-7）
4（2X-3）＞5（X+2）
5、2X＜4
X+3＞0
6、1-X＞0
X+2＜0
7、5+2X＞3
X+2＜8
8、2X+4＜0
1/2（X+8）-2＞0
9、5X-2≥3（X+1）
1/2X+1＞3/2X-3
10、1+1/2X＞2
2（X-3）≤4

The average value of five numbers is 20. If one of the numbers is changed to 40, the average value becomes 25. Find the number

40-（25-20）X5
=40-15
=25

2.34*11—117*0.22

2.34*11—117*0.22
=2*1.17*11-1.17*22
=0

Mr. Wang takes some money to buy books for the school library. He can buy 16 idiom stories or 24 interesting mathematics books with his money. If Mr. Wang buys them, he can buy them
After six idiom stories, how many copies of interesting mathematics can be sold with all the money left?

24 / 16 = 3 / 2, which means that the price of two idiom stories can buy three interesting mathematics books. After six idiom stories, you can buy ten idiom stories or 10 × 3 / 2 = 15. So you can buy 15 interesting mathematics books for all the rest of the money

Fill in the blanks according to the rule: 1,5,14,30,55, ()

91

If 7x + 1 = 15, what is 51-4.5x

7x + 1 = 15
7x = 15 - 1
7x = 14
x = 14÷7
x = 2
By substituting x = 2 into 51 - 4.5X, we get the following result:
51 - 4.5x
= 51 - 4.5×2
= 51 - 9
= 42