5.1. Petya runs twice as fast as Kolya and three times as fast as Masha. On the running track of the stadium, Petya, Kolya, and Masha started at the same time. Petya reached the finish line 12 seconds earlier than Kolya. By how many seconds did Petya finish earlier than Masha?
Answer: By 24 seconds.

Solution: Since Kolya runs twice as slow as Petya, he spends twice as much time covering the distance. Therefore, Kolya ran the distance in 24 seconds, and Petya in 12 seconds. Then Masha ran the distance in $12 \cdot 3=36$ seconds and fell behind Petya by $36-12=24$ seconds.

Comment: Just the answer without explanation - 3 points.

Any text showing that the answer is not just guessed can be considered as an explanation.