Ineed finding the missing angles, show work

What does it mean by solve the exponential equation for x?

Select a graph that have an equation with a < 0

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