Thread: Basic order of operation question

Ok so this is pretty basic:

-8-5(-8+4)
= 12

so you do (-8+4) = -4

then you multiply the brackets, but heres where im confused, why do you 5* -4 =-20 and not -5*-20, because it is a negative 5 before the brackets right?

Originally Posted by ollyrutts

Ok so this is pretty basic:

-8-5(-8+4)
= 12

so you do (-8+4) = -4

then you multiply the brackets, but heres where im confused, why do you 5* -4 =-20 and not -5*-20, because it is a negative 5 before the brackets right?

Hi Ollyruts,

Yes, this is pretty basic. Here are the steps with the order of operations:

[1.] -8 - 5(-8 + 4)

[2.] -8 -5(-4)

[3.] -8 + 20

[4.] 12

So can you do it two ways i.e.

-5(-4) = 20
= -8 + 20
=12

or

5(-4) = -20
-8 - -20
12

is this ok to do?

Yes, although the "- -" without parentheses looks strange! Slightly clearer would be -8- (-20)= -8+ 20.