Answer:she spent 1/8 of her money on the books
Step-by-step explanation:
Let x represent the fraction of his money that he spent on the books.
Mia spent 1/4 of her money on a sandwich. He spent 2 times as much on a gift for his brother as on comic books. This means that the fraction of his money that she spent on a gift for her brother is 2x
Total amount that she spent is
1/4 + 2x + x = 1/4 + 3x = (1 + 12x)/4
Amount that he has left would be
1 - (1 + 12x)/4 = [4 - (1 + 12x)]/4
He had 3/8 of his money left. It means that
[4 - (1 + 12x)]/4 = 3/8
(4 - 1 - 12x)/4 = 3/8
(3 - 12x)/4 = 3/8
Cross multiplying, it becomes
8(3 - 12x) = 12
24 - 96x = 12
96x = 24 - 12 = 12
x = 12/96 = 1/8
