Question

Simplify rational expression

Answer 1

Take - common from either numerator or denominator then both are same 
therefore cut it 

Answer 2

In order to simplify, we want to change the 10 - x to an x - 10.

To do that, we can factor out a -1.

So we have -1(x - 10)/(x - 10).

Now our x - 10's cancel leaving us with -1.