By twice, we mean you add it twice, or ×2.
So we're multiplying by 2, a sum between these two things
- A number that we do not know, so we'll call it x
- The number 5
So the sum between x
& 5 is simply x + 5, and we're multiplying that by 2.
So we're not doing 2x + 5, nor are we doing x + 2×5, because neither of those is "twice the sum" as the question states.
We do 2(x + 5). This tells us that whatever x + 5 turns out to be, we make twice that; and if we were to plug in a number for x, Order of Operations tells us to find the sum before we multiply by two.
Hope this helps,