It would take him 20 minutes. Since the bottom of the chart goes up by 8 each time while the top goes up by two, only adding half of 8 (4) on the bottom would make the most sense. Since those numbers go up by two. Going up or down one would make you have to add or subtract 4 to get to in between numbers.
Look at the first columns, and it tells us that Charlie runs 2 laps in 8 minutes. Then simply divide by two, then you'll get that Charlie runs 1 lap in 4 minutes. So for five laps, multiply 4 by 5, which is 20.
