Simplify brackets
-8a - 6 - 10a - 2 + 5a
Collect like terms
(-8a - 10a + 5a) + (-6 - 2)
Simplify
<u>-13a - 8</u>
Yes it is, that math is fully correct!

These are all approximate decimal versions of the given numbers' square roots. If you need help rounding the decimals to a certain number of digits, let me know.
I hope this helps :)
Its ok buddy your answer is C