Haven’t been able to figure this out, can someone help?

7x+8y=-18, 4x-9y=-3 solve the system of equations

At the beginning of year 1, carlos invests $600 at an annual compound interest rate of 4%. he makes no deposits to or withdrawals from the account. which explicit formula can be used to find the account's balance at the beginning of year 5? what is, the balance?

Which is the best estimate of the product of 0.9 x 0.88? 0 0.25 0.5 1