4000 principle earning 6% compounded annually after 5 years

Tomas used 3 1/3 cups of flour and now has 1 2/3cups left. which equation can he use to find f, the number of cups of flour he had to begin with? f+3 1/3=1 2/3 f-3 1/3=1 2/3 3 1/3f=1 2/3 f/3 1/3=1 2/3

What adds to be the bottom number but also multiplies to be the top number with 8 on the bottom and 15 on top

Ineed to know how to write question one in mathematical terms