Gordon rode his bike at 15 mph to go get his car. He then drove back at 45 mph. If the entire trip took him 8 hours, 9 miles far away was his car.
Solution

He then drove back at 45 mph, so the time it took him to return can be calculated similarly:
t2 = d / 45

The total time for the trip is given as 8 hours:
t1 + t2 = 8

Substituting the expressions for t1 and t2, we have:
d / 15 + d / 45 = 8

To simplify the equation, we can find a common denominator of 45:
3d / 45 + d / 45 = 8

Combining like terms:
(4d / 45) = 8

To isolate d, we can multiply both sides of the equation by 45/4:
d = (8) * (45/4)

Calculating the value:
d = 360/4
d = 90