Are you on this minute?

You start them both at the same time. When the 5 minute timer ends, you restart the 5 minute timer and stop it when the 7 minute timer finishes (leaving 3 minutes). You reset the 5 minute timer, let...

2 hours and 18 minutes

Minutes? 45 minutes in 45 minutes. If you meant seconds... 45 x 60 = 2700

70, geinius...The answer might be more convincing is spelt "genius".