Question 571922
Let x = the amount of the refund Dorothy invested at 7% per annum. The remainder, (3x), she invested at 11%.  The interest earned on these two amounts can be expressed as:
0.07x+0.11(3x) = 120 Simplify.
0.07x+0.33x = 120 Combine like-terms.
0.4x = 120 Divide both sides by 0.4
x = 300
Dorothy invested $300 at 7%