We are given the amount of books in three different ways: a decimal, percentage, and fraction. If we express these values in the same format, they will be easy to compare.
0.3 is equal to 30 out of 100
25% is equal to 25 out of 100
Finally the numerator and denominator of 7/20 can both be multiplied by 5 to get 35 out of 100.
35 < 30 < 25, therefore children books take up the most space.