At brian's bookstore three tenths of the show some mysteries 25% shelves hold travel books, and 7 over 20 of the shelves hold children's books. which type of book covers the most shelf space in the store?

Children's books cover the most shelf space in the store.

Mysteries = 3/10
Travel = 25%
children = 7/20

Based on the problem, the total number of shelves in the bookstore is 20.
Therefore:

Mysteries = 3 / 10 * 20 = 6 shelves
Travel        = 25%  * 20 = 5 shelves
Children    = 7/20  * 20 = 7 shelves

Total shelves occupied by the three types of stories is 18.

Children's books cover the most shelf space in the store.