Guys pls help me I don’t have much time and don’t answer with link thanks

If f(x)=x^3 and g(x)=2x+7 when g(x)=-5

Which of the following expressions is equal to 2x^2+8

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