1. State the problem: Thirdy bought a cellphone for 15291.50 after a 15% discount. We need to find the original price and the discount amount. 2. Let the original price be $P$. 3. Since the cellphone was sold at a 15% discount, Thirdy paid 85% of the original price. 4. Write the equation: $$0.85P = 15291.50$$ 5. Solve for $P$: $$P = \frac{15291.50}{0.85} = 17990$$ 6. Calculate the discount: $$\text{Discount} = P - 15291.50 = 17990 - 15291.50 = 2698.50$$ 7. Final answer: The original price was $17990$ and the discount was $2698.50$.