Hey there!
The price of the pair of jeans is now 125% of what it used to be. 125% is now going to be considered our new 100%, and 100% will now be considered 80% of the new price. I got 80% by dividing 100 by 125 to get 0.8.
All we need to do is multiply our 80% (in decimal form by dividing the percentage by 100) by our new 125% price.
80% = 0.8
$25.00 × 0.8 = $20.00
The old price before the increase was $20.00.
Hope this helped you out! :-)