sonya spent 3/8 of her money and had $15 left. how much money did she orginally start with?

Answer 1

If Sonya spend 3/8 of her money, she has (1-3/8)=5/8 left.

Use proportions:
5/8 : $15
1 : $x

Use cross multiplication to get:
$x=$15*1÷(5/8)
=$15*(8/5)
=$24