(78 - 28) / 2
---------
  50      / 2
  -----------
      25

(2 + 6) / 2 - 9    
-------
   8    / 2 - 9
   --------
        4   - 9
        -------
           -5

Nested Parentheses

Sometimes in a complicated exression one set of parentheses is not enough. In that case use several nested sets to show what you want. The rule is:

The innermost set of parentheses is evaluated first.

The expression is evaluated starting at the most deeply nested set of parentheses (the "innermost set"), and then working outward until there are no parentheses left. If there are several sets of parentheses at the same level, they are evaluated left to right. For example:

( ( ( 32 - 16 ) / ( 2 * 2 ) ) -  ( 4 - 8 ) ) + 7
    -----------

( (     16      / ( 2 * 2 ) ) -  ( 4 - 8 ) ) + 7
                  ---------

( (     16      /     4     ) -  ( 4 - 8 )  ) + 7
  ---------------------------

(               4             -  ( 4 - 8 )  ) + 7
                                  -------

(               4             -      -4     ) + 7
---------------------------------------------
                    
                     8                        + 7
                     ----------------------------

                                  15

Ordinarily one would not do this in such detail, but would skip a few steps.

(12 / 4 ) + ( 12 / 3)