We know that Earl can run 50 meters in 20 seconds. That means he can run 150 meters in one minute and 9,000 meters (or 9 kilometers) in one hour. 50 meters / 20 seconds = ? meters / 1 second
50 meters / 20 seconds = x / 1 second
(50 x 1) = (20) (x)
50 = 20x divide both sides by 20 to get the "x" alone
The answer should be D since after 5 am to 7 am only two hours have passed so x=2, and then you plug in the x as 2 and solve it. You might get not around answer like 39.785 but when you round it, it would be 40.