+24 + 3 * -4
      ------
+24 +   -12
-----------
     12

Arrange what you want with Parentheses

To say exactly what numbers go with each operator, use parentheses. For example

-1 * ( 9 - 2 ) * 3  

means do 9 - 2 first. The "( )" groups together what you want done first. After doing the subtraction, the ( 9 - 2 ) becomes a 7:

-1 * 7 * 3  

Now follow the left-to-right rule for operators of equal precedence:

-1 * 7 * 3  
------
  -7   * 3
  --------
     -21