John drove 450 miles in 8 hours. he averaged 50 miles per hour on the highway and 60 miles per hour on the turnpike. how many hours did he drive on the highway?

Total distance John drove=450 miles

total time=8 hours

let the number of hours he drove on highway be x, number of hours he drove on turnpike will be (8-x) hours

since

distance=speed*time

distance traveled in highway=50x

distance traveled in turnpike=60 (8-x)

thus the total distance will be:

50x+60 (8-x) = 450

simplifying the above

50x+480-60x=450

-10x=450-480

-10x=-30

thus

x=3 hours

Thus he drove on highway for 3 hours.