Though people are usually taught that putting a number next to parentheses means multiply, what it actually means is the number is a FUNCTION OF what's in the parentheses... meaning that in the above scenario, two is a function of 1+2, meaning you apply the 2 to what's in the parentheses (1+2, or 3) giving you 6.
Meaning it's 6/6 = 1.
You can't really say it's (6/3) * (1+2), because that's extrapolating parentheses to indicate multiplication, when they really don't it's just an easier way of thinking of it (which in this case is inaccurate). That's why using PEMDAS or what have you doesn't work here, because there's no "M".
edit: to be a little more clear, let's say you have the function 6/f(x). Looking at it like that, most of you would probably agree that you can't separate f from x. Well, if f=2 and x=3, you STILL can't separate f from x, even if we've assigned it a constant.
