Evaluate 4x - y if x=3 and y=-2

What you do is to start writing the expression 

            4x - y

character by character, except when you
come to the letter x, you don't write x, 
but instead write (3) in parentheses.  
And when you come to the letter y, you 
don't write y, but instead write (-2).

So what you have when you do that is

         4(3) - (-2)

Now you change the 4(3) to 12, so you have on 
the next line:

          12 - (-2)

Then you have the subtraction of a negative two.
So you change this to an addition, and write on the
next line:

            12 + 2

Then you add those and get

             14

as your final answer.

So the lines on your paper should look like this:

            4x - y
            4(3) - (-2)
            12 - (-2)
            12 + 2
            14

Edwin