26-d=8 I need help on this pls

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?

Math i have no idea how to do a and b

The height of a box can be found by dividing its volume by the area of its base, bottom. what is the height of a box that has a volume of 26.35 cubic centimeter and a base area of 4 1/4 square centimeter?