I am VERY confused on this question. Can someone help me?

At the newest animated movie, for every 9 children, there are 4 adults. there are a total of 39 children and adults at the movie.

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?

Find the value of x. give reasons to justify your solutions! c ∈ ae