The story books in the school library are one fourth more than the science and technology books, and the story books are equivalent to the number of each technology book

The story books in the school library are one fourth more than the science and technology books, and the story books are equivalent to the number of each technology book

five-fourths
If the science book is 1, the story book is 1 + 1 / 4 = 5 / 4
So storybooks are 5 / 4 of science and technology

The school bought a batch of science books and divided them into three classes. Class a got 42% of these books, class B got 5% of class A, and class C got 2 less than class B. how many science books are there in all?

A 42%
B: 42% × 5 / 7 = 30%
C: 1-42% - 30% = 28%
A total of books: 2 (30% - 28%) = 100

The school assigned 360 science and technology books to class A, class B and class C. class A's 1 / 2 equals class B's 1 / 3 equals class C's 1 / 4. How many books did class A, class B and class C get

It's a pity that it's not y-pei
The ratio of the three classes to the books is: (1 / 2): (1 / 3): (1 / 4) = 2:3:4
Grade A: 360 × 2 / (2 + 3 + 4) = 80
Score of class B: 360 × 3 / (2 + 3 + 4) = 120
Grade C: 360 × 4 / (2 + 3 + 4) = 160

The school divided 360 story books into three classes: Class A, class B and class C. one half of class A and one third of class B were equal to one fourth of class C. class A and class B and class C got more story books
I want simple formula, don't copy, don't equation, I want formula

One half of class A and one third of class B are equal to one fourth of class C
therefore
A: B = 2:3
B: C = 3:4
therefore
A: B: C = 2:3:4
therefore
A score = 360 ÷ (2 + 3 + 4) × 2 = 80
B = 360 △ (2 + 3 + 4) × 3 = 120
C = 360 △ (2 + 3 + 4) × 4 = 160

There are 630 science, technology and story books in the school library
Among them, science and technology books account for 20%, and the school has bought a batch of science and technology books. At this time, science and technology books account for 30%?

There are always story books: 630 × (1-20%) = 504
After the school bought a batch of science and technology books, storybooks accounted for 1-30% = 70%
Therefore, there are now a total of science and technology books and Storybooks: 504 ／ 70% = 720

There are 125 comic books in the school library, which is equivalent to one third of story books. How many story books are there

Storybook × 1 / 3 = Comic Book, 125 ／ 1 / 3 = 375

35 + 12 * 40-20 = 1000

I don't know if this is an equation
（35+12）*（40-2）0=100（0）
47*0=0
0=0

How to bracket 7x9 12 / 3-2 to be equal to 35

7×[(9+12)/3-2]=35

12 + 12-12 + 12 △ 12 = 12, add brackets to make the formula true

12+12（-12+12）÷12=12
That's the minus sign in the middle. That's it

Add brackets in the formula 320 + 480 / 40 * 2 - 40 = 20 to make the equation hold

(320+480)/(40*2-40)=20