Sally and her husband Jim left their house at the same time traveling in the same direction. Sally drove at 55mph and Jim drove at 65mph. How many hours was it before Jim was 100 miles ahead of Sally?

It will take 10 hours.

Step-by-step explanation:

We know distance = rate * time

Sally's rate = 55

Jim's rate = 65

We want Jim to be 100 miles ahead of Sally

The time will always be the same.

d = Sally's distance

Sally

d = 55t

Jim

d+100 = 65 t

We know have 2 equations with 2 unknowns. Substitute d = 55t into Jim's equations

55t + 100 = 65t

Subtract 55t from both sides.

55t-55t + 100 = 65t-55t

100 = 10t

divide each side by 10

100/10 = 10t/10

10 = t