Kathy and Brian drove a total of 750 miles in 12 hours. Kathy drove the first part of the trip at 65 mph and Brian drove the rest of the trip at 55 mph. For what length of the time did Kathy and Brian drive?

Kathy drove the first 9 hours of the trip and Brian drove the last 3 hours.

Step-by-step explanation:

Let's review the information given to us to answer the question correctly:

Total distance of the trip = 750 miles

Time of the trip = 12 hours

Speed of Kathy = 65 mph

Speed of Brian = 55 mph

2. For what length of the time did Kathy and Brian drive?

Let's solve the problem, this way:

x = Time in hours Kathy drove

12 - x = Time in hours Brian drove

Now, let's write our equation to solve for x:

65x + 55 (12 - x) = 750

65x + 660 - 55x = 750

10x = 750 - 660

10x = 90

x = 90/10

x = 9 ⇒ 12 - x = 3

Kathy drove the first 9 hours of the trip and Brian drove the last 3 hours.