Answer:
$1
Explanation:
To find out how much more money Olivia spent per apple, we need to find out how much each spent on one apple.
Cassie:
2 apples --- $4
1 apple --- $4 ÷ 2 = $2
Olivia:
5 apples --- $15
1 apple --- $15 ÷ 5 = $3
Difference per apple = $3 - $2
= $1