This question I do not understand .someone please explain to me please I need it ASAP!

Provide an example of a trigonometric function and describe how it is transformed from the standard trigonometric function f(x) = sin x, f(x) = cos x, or f(x) tan x using key features.

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?

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