hi!
so the original equation is (x^2 -121) / x+ 11.
Those two equations look similar...
well, we know that the top equation looks like a^2 - b^2, and that equation iis equivalent to this equation: (a+b)(a-b).
So if we factor that out, we get:
( (x + 11) * (x-11) )/ (x + 11)
we can cancel the x+11 on the top and the x+11 on the bottom out.
that leaves us with x-11.
Hope this helped!