Answer:
15.1667 hours (15 hours and 10 minutes)
Step-by-step explanation:
Using the concept of "distance = speed * time", we can formulate equations to solve this problem.
Let's call Leon's speed X, Michael's speed Y and the length of the driveway D.
If leon takes 13 hours alone, we can write the equation:
D = X * 13
If Michael helps Leon, we have this equation:
D = (X+Y) * 7
(The total speed is the sum of their speed, as they are working together)
Making the first equation equate the second, we have:
13*X = 7*X + 7*Y
7*Y = 6*X
X = (7/6)*Y
If we use this value of X in the first equation, we have:
D = 13*X = 13*(7/6)*Y = 15.1667*Y
So we have that Michael would take 15.1667 hours (15 hours and 10 minutes) to seal the driveway alone.
