Write a radical expression y^1/3

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

Rewrite so the subject can be y in the formula d=m-y/y+n

Pls the last one and it has to be like number 6