#### Answer

Monica overtakes Sandy after 9 hours.

#### Work Step by Step

Sandy leaves a town traveling in her car at a rate of 45 miles per hour.
Let t represent the time Sandy travels until she is overtaken by Monica.
Since Monica leaves town one hour later than Sandy, the time she travels until she overtakes Sandy is t-1.
Because the second car is to overtake the first car, the distances must be equal.
So: 45 $\times$ t = 50 $\times$ (t - 1)
45t = 50t - 50
5t = 50
Divide both sides by 5.
t = 10
Since Monica overtakes Sandy after t-1 hours, and t = 10, then we know that Monica overtakes Sandy after 10-1 = 9 hours.