Original Price = $42
Discount = 25% ---------> 25% is discount because it says 25% off!!!
Now,
Sale price = original price - discount % of original price
= 42 - 25% of 42
= 42 - (25/100) * 42
= 42 - 0.25 * 42
= 42 - 10.5
= 31.5
So, the sale price is $31.5