## Elementary Algebra

Let X represent the amount invested at 3%. Thus, the remainder, which is 2100 - X, is invested at 5%. The interest earned by the 3% investment is equal to 3% $\times$ X = 0.03X. The interest earned by the 5% investment is equal to 5% $\times$ (2100 - X) = 105 - 0.05X. Since the interest earned by the 5% investment is 51 dollars more than the interest from the 3% investment, we set up the following equation: 105 - 0.05X = 51 + 0.03X 105 = 51 + 0.08X 54 = 0.08X Divide both sides by 0.08. X = 675 675 dollars are invested at 3%. 2100 - 675 = 1425 are invested at 5%.