Order of Operations

If you have an expression that has adds, subtracts, multiplies, divides and (maybe) parentheses, then this is the order that you do them in:

  1. Things inside parentheses "( )" first ...
  2. Multiplies and divides next ...
  3. Adds and subtracts last
Example:

Evaluate for a = 3, b = 6, h = 8:
(a + bh) - b/2

First, let's put in the numbers:
(3 + 6 x 8) - 6 / 2

Now, we do the things inside the parentheses,
and within the parentheses, we do the multiply first:

(3 + 48) - 6 / 2

Finishing up the things inside the parentheses and then removing them, we get:

51 - 6/2

Next, we do the divide:

51 - 3

Then we subtract:

48


Notice that if you do the operations left-to-right, ignoring the order rules, you get a different (wrong) answer:

3 + 6 x 8 - 6 / 2 =
9 x 8 - 6 / 2 = 66/2 = 33