Last year ms. diaz invested $9,000. Some of her money was invested in stocks paying 6% annually and the rest was invested in bonds paying 7.5% annually. She received a total of $600 from these investments for the year. How much did she invest in the stocks paying 6%?

To solve the problem you would have to do the equation "Balance = Principle (1 + rate) ^Time" You are trying to figure out the balance and the first thing you do is find the principle. In this case the principal is $9,000 because that's how much money she invested. After that you need to figure out the rate. To figure out the rate u would have to divide 6% by how it's compounded. For this problem, it's compounded anually so you don't have to do anything. Then the time is a year. So you set up the problem like this ... B = 9,000 (1+.06) ^1 then you should get 9,540 then you subtract that by 9,000 and you answer should be $540