## Elementary Algebra

Let s represent the original price. We can use the following guideline to solve this problem: Original selling price - Discount = Discount sale price s - 10% $\times$ s = 121.50 s - 0.1s = 121.50 0.9s = 121.50 Divide both sides by 0.9: s = 135 The original price of the monitor was 135 dollars.