3.3 Solving Equations Involving only Addition and Subtraction

We will now apply what we have learned so far to solve some very simple equations, ones in which you can spot the answer. We will use special techniques which will seem unnecessary for such simple problems. However, you have to learn the techniques, because you won’t be able to spot the answer to the more difficult equations you’ll meet later.

Suppose we want to solve the equation x + 2 = 5. This means we want to find the value of x which makes the statement true. Obviously the solution is x = 3 because when you replace the letter x by the number 3 you get 3 + 2 = 5, which is true.

Now we will use a procedure to do this.

The aim in the solution of any equation (or the transposition of any formula) is to isolate the variable in which you are interested. As far as our equation is concerned, we have to get x on its own on one side of the equation. This means getting rid of the 2 on the left.