First calculate the sale price.
Since they are 25% off, he is paying 75% of the original price.
Multiply 49.99 by 75% ( 0.75) for the sale price.
49.99 * 0.75 = 37.49 ( amount the roller blades are on sale for)
Now multiply the sale price by 5.5% (0.055) to find the amount of tax, then add that to the sale price:
37.49 x 0.055 = 2.06
37.49 + 2.06 = $39.55 total cost.