Step 8: Set the selling price equal to $80: 0.80 * x = 80.
Step 9: To find 'x', divide both sides of the equation by 0.80: x = 80 / 0.80.
Step 10: Calculate the value: x = 100.
Step 11: Conclude that the marked price is $100.
Percentage Discount Calculation – Understanding how to calculate the selling price after applying a percentage discount to the marked price.
Algebraic Manipulation – Using algebra to solve for the marked price by setting up an equation based on the relationship between marked price, discount, and selling price.