Let X be the original price of the shoes. The discounted price is X - X * 75% = 0.25 * X = $51. The original price of the shirt was X = $51 * 4 = $204.
This justifies what answer for what question? Q & A:
I bought a pair of shoes for $51. The shoes were already marked 75% off. What is the original price of the shoes?
204