Question

How do you solve equations that contain addition or subtraction?

Answer 1

Any equation given, with a variable, could be solved by applying the inverse operation. 

Example:-

4 + x = 8
-4        -4

x = 8 -4
x = 4

Answer; x = 4

Answer 2

To learn the basics I would suggest using this simple model to solve. Remember, that you can add, subtract, multiply, or divide anything to both side of the equal sign.
Ex. 5 + 5 = x
     -5       -5

Now, let's try a real problem:
         
            10 + x = 15
Now, I know this may seem to be an easy problem, but by using the method I am about to show you, you will be able to solve any addition, subtraction, even multiplication, and division equation!
      This would be how you solve:           
                10 + x = 15
                 -10         -10
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                        x = 5
 
Hope this helped!