Stan wants to arrange his books in order of size. Half of the books are medium, 2/10 are large and 12 are small. What is the total number of books Stan has?

Answer 1

7/10 of the books are not small.

3/10x = 12
x = 12 / (3/10)
x = 12 * (10/3)
x = 120/3
x = 40

Answer 2

let, total number of books= X
Small= 12
Remaining books = X-12
now,the remaining books comprise:
1/2X= Medium
2/10X= Large
Therefore,
1/2X+2/10X=X-12
Solve for X and you will get the answer!!