Yes, if it were written 6 / 2 x 3, the answer would be 9.
But it isn't written that way. And when you write 2(1+2), the whole thing is an expression that needs to be treated as a unit in terms of any other operations.
The expression 2(2+1) equals to 6 and needs to be treated as if it were the number 6.
If you were using letters a and b instead of the 2 and 1 in the parentheses, it would be 2(a+b). This is a tidy way of writing (2a + 2b) because it's treated as a unit. Plugging the numbers back in, it would be the sum of 2x2 (4) and 2x1 (2), i.e., 6.
6 divided by 6 is 1.
