problem solving rational numbers

Question

Matt spent 3/10 of his allowance on projects, 2/5 on snacks, and 2/3 of the remainder on books.What is the fraction of his allowance was spent on books?

Answer 1

He spent 2/5 +3/10 which is 7/10 of his allowance. This leaves him with 3/10 ( 1- 7/10) If he spends 2/3 of this remainder this is (2/3) x(3/10) = 6/30 = 1/5 or 20 percent