What does 15cubed look like in exspanded form

Don't know how to find x given these segment lengths

At the beginning of 1974/75,2 years a man invested #2000 in a bank at 12.5% compound interest, if it degree #650 at the end of each two years to pay his son's school fees, after payment of interest to pay his son's school fees, how much did he have left at the beginning of the 1978/79 school year?

Evan went to the park and saw for animals each animal was either a duck or dog if he saw a total of 14 legs how many of each animal did he see