[quote=kingfisher]maths is a hard nut to crack....

http://www.youtube.com/watch?v=vU5LoCLGMdQ[/quote]

Am dead...

Posed this same question to my Finance Manager (man) and Accountant (lady) today morning.

Finance Manager = 13 with no method and wrote (QED).

Accountant = 17 with method and even arrows pointing left at the last stage of addition and substration.

I wonder who needs to be fired here?

Wazuans the correct answer is 13.

You are supposed to introduce brackets (parenthesis) to the numbers to be multiplied or divided.

I think the problem depends on the addition and subtraction that is:-

21-6+2

if your begin with subtraction:-

(21-6)+2
15+2

you get 17

if you begin with the addition:-

21-(6+2)
21-8
you get the 13

so if BODMAS stands for Brackets of Division Multiplication Addition and Subtraction and should be followed in that order. It would mean that those who first add the 6 to the 2 to get 8 which is subtracted from the 21 to give the 13 are right