A mother earned ​$12500.00 from royalties on her cookbook. She set aside​ 20% of this for a down payment on a new home. The balance will be used for her​ son's future education. She invests a portion of the money in a bank certificate of deposit​ (CD account) that earns​ 4% and the remainder in a savings bond that earns​ 7%. If the total interest earned after one year is ​$600.00 how much money was invested at each​ rate?

20% of $12500.00 is 0.20*12500 = $2,500

The new balance is 12500 - 2500 = $10,000

Let

'x' represent the money invested in a CD account at 4% annual percentage rate

'y' represent the money invested in saving bods at 7% annual percentage rate

x + y = 10,000

0.04x + 0.07y = 600

........

click here to see the system of equations solved for x and y

........

x = $3,333.33

y = $6,666.67

$3,333.33 was invested at 4% and $6,666.67 was invested at 7%.