Answer
(5 + 7) · 2
Step-by-step explanation
If we take a look at PEMDAS or BEDMAS whichever one you were taught, multiplication comes before addition. (And unless you are in 2nd grade, you will know that "times" means multiplication, and sum is the result of an addition problem.)
P = Parentheses B = Brackets/Parentheses
That means that anything in parentheses or brackets comes first, no matter what type of problem it is. So, if we add 5 and 7 and then multiply it by two and just rephrase that, we get 2 times the sum of 5 and 7.