78 - 12 / 4            2 + 6 / 2 - 9

    75                      -4

Evaluation by Rewriting

When evaluating an expression it can be helpful to do it one step at a time and to rewrite the expression after each step. For example:

78 - 12 / 4

Here, the division is done first since it has highest precedence. So rewrite the expression by replacing the division subexpression with its value:

78 - 3

Now evaluate the resulting expression:

75

Often the whole process is written like this:

78 - 12 / 4
     ------
78 -    3
---------
   75

The lines show what is done at each step.

24 / 2  - 8