The two friends will be 150 miles apart, when the sum of the distances covered by the them is 150 miles.
distance = speed x time.
Let the time covered when they are 150 miles apart be x, then:
40x + 35x = 150
75x = 150
x = 150/75 = 2.
Therefore, the two friends will be 150 miles apart in 2 hours.
