a total investment of $9,600 is made into two savings account. One account yields 7% simple interest and the other 9% simple interest. He earned a total of $816.00 interest for the year. How much was invested in the 7% account?

Solution:

7% investment:x

9% investment:9600-x

So

7%x+9%(9600-x)=816

x=2400

So

$2400 was invested in the 7% account