Explanation:
your text misses some parts.
so, there is no clear way to tell you the correct answer option. but there are some indications what is more likely your teacher wants to see as an answer, when we look at the individual options.
x² + 16x + 64 = 800
is the same as
(x + 8)² = 800
and then
x + 8 = sqrt(800) = 28.28427125...
x = 20.28427125...
not a nice number, but yes, a possible solution.
x² + 8x + 16 = 800
is the same as
(x + 4)² = 800
x + 4 = sqrt(800) = 28.28427125...
x = 24.28427125...
again, not a nice number, but yes, a possible solution.
I ignore "none of the choices are correct". again you did not provide enough information to make that call, as we have already 2 possibly valid solutions.
x² + 16 = 800
x² = 784
x = sqrt(784) = 28
that is a "nice" number and a possible solution.
I would therefore bet on this answer, although, as mentioned, it is not clear what we actually try to find out.