system of equations

Dear all,
Is there anyway to figure out this math problem? Thank you very much!

Write the system of equations that will solve the following problem. Just write the system. Don't solve it. Use the variables U ans S as indicated below.

A lottery player has won $90000. She would like to invest a portion of the winnings in utility bonds which pay 8% interest and the rest of her winnings in a saving account which pays 3% interest. How much money should she place in each of these investments so that the interest earned from bonds is three times the interest earned from saving?

Let U be the amount of money, in dollars, that she’ll invest in utility bonds.
Let S be the amount of money, in dollars, that she’ll invest in the savings account.

Thanks a lot!