Plz help me this is 7th grade math

Solve the system of equations. y= 2x y= x^2 - 15

Look at the following graph of the given equation. determine whether the equation is a function. explain why or why not.

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?