Answer: She's wrong.
Explanation:
Numbers of hours used in solving homework last week = 15
Numbers of hours used in solving homework this week = 18
Percentage increase = (18 - 15) / 15 × 100
= 3/15 × 100
= 1/5 × 100
= 20%
Since Maxie said that she spent 120% more time doing homework this week, she's wrong. She only spent 20% more.