Investment task algebra

Question

Jake invested some money on three different accounts, If he invested $7500 in an account with an annual return of 8% and $4000 in an account earning 8.9%, how much money, to the nearest dollar, did he invest at 8.25%, if he earned %1166.30 in a year?

 

Can you please help ?

Answer 1

7500(.08) + 4000(.089) +x(.0825) = 1166.30

multiplying the amount of money times the interest rate gives you the interest.  When you add them up it gives you the total interest

 

600+356 + .0825x = 1166.30

0.0825x = 210.30

divide by 0.0825 and get

x = 2549.09