A mother wants to invest $ 12,000.00 for her sons education. She invests a portion of the money in a bank certificate of deposit (CD Account) which earns 4% and the remain saving bond that earns 7%. If the total interest earned after a year is 720.00, How much invested in the CD. Round to the nearest cent.

1 answer

amount invested at 4% --- x
amount invested at 7% ---- 12000-x

.04x + .07(12000-x) = 720
I would multiply each term by 100

4x + 7(12000-x) = 72000

solve for x, it is straightforward form here