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.If he saved the rest, what fraction of his allowance did she save?

Answer 1

3/10 + 2/5 = 7/10 = fraction spent on projects and snacks

3/10 is the remainder. 2/3 of 3/10 = 2/10 = fraction spent on books

7/10 + 2/10 = 9/10 = the fraction spent on projects, snacks and books

Matt saved 1-9/10 = 1/10 of the allowance