[GingisK]

Division and multplication are handled from left to right unless a parenthetical expression is used.

You should have the following:

48/2(9+3)=x
48/2*12=x
24*12=x [Left to right]
x=288

[GingisK]

Uh oh.

That 2(9+3) really does mean that 2*(9+3) must go first!

We computer guys aren't allowed to imply operators, but the old math rules should apply.