25% is equal to 1/4.
Therefore, you divide $51 by 3 as 1/4 of the price has already been discounted.
That comes out to $17 p[er 1/4 of the jeans.
You multiple $17 by 4 to get 100% (the full price) which would be $68. So you're answer is, $68 was the original price.
