Question

which expressions are equivalent to 2(4f+2g)

Answer 1

The expression would be 8f + 4g after distributing

Answer 2

Well in this problem you have to multiply the 2 in the outside the parenthesis by the numbers inside and since the
$2 \times 4f = 8f$
$2 \times 2g = 4g$
So your answer is
$4g + 8f$

You don't add them because they don't have the same variable