The right expression to calculate how much money will be in an investment account 15 years from now if you deposit $4,000 now and $7,000 nine years from now and the account earns a compound interest rate of 12% is;

F= 4,000(F/P, 12%, 15) + 7,000(F/P, 12%, 6)

F= 4,000(F/P, 12%, 15) + 7,000(F/P, 12%, 15)

F= 4,000(F/P, 12%, 15) + [7,000(F/P, 12%, 6)(F/P,12%,15)]

F= 4,000(P/F, 12%, 15) + 7,000(P/F, 12%, 6)