no, it's not a square root that we need to identify
Part A: 6m + 12 + 42m, which combines to form 48m + 12. Another expression is 12 + 48m, because using the commutative property of addition, it is equivalent.
Part B: As I stated earlier, using the commutative property of addition, your expression 12 + 48m is equivalent to 48m + 12.
Part C: If you substitute 2 for m, you will get 108. If they are talking about the main equation, then if you substitute 2 for m, you will have 6(2 + 2 + 14) = 108.
When the exterior sides of two adjacent angles form a straight line or in this case form an opposite ray then, the angles are supplementary. The supplementary angles are those whose sum of the measures is 180°. Thus, the answer to this is letter B.