Question 3659
akr's answer is absolutely correct, HOWEVER...

Note that when you have an equation of the form:

{{{A^2-B^2}}} 

it is refered to as the difference of two squares and can be factored like this:

{{{(A+B)(A-B)}}}

Here we can let:

{{{A^2=(x-5)^2}}}

and 

{{{B^2=100}}}

Then this factors to:

((x-5)+10)((x-5)-10))=0 

and simplified to:

(x+5)(x-15)=0

So either x+5=0 or x-15=0  thus x=-5 or x=15.

Watch for the difference of two squares they show up all the time and they make some problems much easier.