You did  just fine with setting up the equation:



Then you factor the parentheses on the right:



You can divide both sides by  because
since you are told that a and b are two unequal
numbers, a-b is not 0, so you can divide by it:



 



Divide through by 





  

So you don't know what a and b are, and there is 
no way to find out. However that doesn't matter 
because you already have their sum, a+b, which 
is 515 pairs of jeans.

Edwin