Question

twice the sum of x and y

Answer 1

Twice the sum of x and y = 2(x+y)

the sum of twice x and y is too sloppy a statement to even be considered mathematical, but...TECHNICALLY...I would have to translate it as 2x+y

So when you represent them mathematically, your answer is obvious:

2(x+y) does not = 2x+y

At its sloppiest translation, considered to be 2x + 2y, they will be the same, but that is NOT technically how I would translate it...which is why we should always express mathematical expressions mathematically, to avoid this potential for ambiguity.

Answer 2

twice = 2
sum = +
of = multiplication
and you have your variables x and y => x+y