How do you arrive at the answer for: 9 - (3x2) +8? Is it 11 or 5?

Question

I am confused about what ORDER is used to determine the answer.  I thought it was: do what is in parentheses, then either add/subtract from left to right.  My granddaughter states after arriving at the "6", you add it to the 8, then subtract 9 from the total and get 5.  I don't see where this is going strictly from left to right.  Help!

Billie

Answer 1

The precedence rules ("order of operations") does follow P-E-M-D-A-S ("Please Excuse My Dear Aunt Sally") as follows:

 

  1]  Parenthesis

  2]  Exponentiation

  3]  Multiplication or Division (left-to-right)

  4]  Addition or Subtraction (left-to-right)

 

Extra notes:

   Re-apply P-E-M-D-A-S within Parenthesis if it is a complex expression.

   Re-start each scan after performing any replacement.

   Some expressions assume multiplication, so  (a+b)(c+d) means (a+b)*(c+d).

   A unary "+" or "-" [no value preceding it] assumes that 0 is included, so "-a-b" means "(0-a)-b"   [one unary, one subtract], not "-(a-b), which is (0-a)+b and also equals (-1)*(a-b)"

 

 

In the expression, "9 - (3x2) +8." something is subtracted from 9, not subtract 9 from something.

 

 

Answer 2

Remember the abbreviation "PEMDAS", which stands for "Parentheses, Exponents, Multiplication and Division, and Addition and Subtraction".

 

9 - (3x2) +8

Parenthesis first

9 - 6 + 8 = 11

Then it's addition and subtraction.

The 6 is negative or what is being subtracted. Addition and subtraction have the same rank so you operate from left to right, the same as reading.