Let's start with an easy one:

Solve 

We can just look at it and see that  x = 10...

But, what if we didn't see that?  What would we do?

Here's the Algebra trick:

We'll add 3 to both sides!

*Remember the see saw?
Whatever we do to one side of the equation,
we have to do to the other side.

Why did we ADD 3?

             To undo this!  + is the opposite of -

The goal is to get the x alone.  Just imagine that Mr. X hasn't showered in a few weeks and everyone wants to get away from him.  It's your job to help.