let

d = 24 mi the distance

v = 40 mph the average speed

t = the time that we need to find

v = d/t

24/t = 40

t = 24/40

t = 0.6 hr

t = 0.6*60 min

t = 26 min

it takes 26 minutes to drive 24 miles with average speed of 40 mph.