Rate in which puzzles are solved:
Maya- 6 minutes per puzzle or 6/1
Amy- 7 minutes per puzzle or 7/1
If Maya and Amy had the same amount of puzzles to solve, Maya would finish first considering it takes Maya just 6 minutes to finish a puzzle as opposed to the 7 minutes it takes Amy.
Explanation: Divide 30 minutes by the 5 puzzles maya completed, to find out Maya does each puzzle in 6 minutes. Then divide 28 minutes by the 4 puzzles Amy completed, to find out it took her 7 minutes per puzzle.
Hope this helped :)