How does writing equivalent equations you solve a system of equations?

Pls me this is due today and i need i will make brainliest if you me answer correctly and i will report if you try to give me a dumb answer.

Kevin is an insurance salesman. when he sells a policy, he makes 20 percent of the policy premium (p) up front; then each year the policy is active, he receives 15 percent of the original premium. which equation could be used to figure his total commission on a policy that has been active for five years? c=0.80p c=0.20p + 0.15p c=0.35p + 4(0.15) c=0.95p

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3