Is this equation an identity? 100 - 7 = 90

For f(x)=2x+1 and g(x)= x^2 -7, find (f•g)(x)

Math it's appreciated. (picture provided)

Cody started biking to the park traveling 15 mph, after some time the bike got a flat so cody walked the rest of the way, traveling 4 mph. if the total trip to the park took 6 hours and it was 46 miles away, how long did cody travel at each speed? solve using rate times time= distance