You are correct. The answer is choice C.
The other choices A, B, D have each side add up to 180 degrees either because the angles are a linear pair (adjacent and supplementary) or because the angles are same side interior angles. Same side interior angles are supplementary if a transversal line cuts through a pair of parallel lines as so happens in this diagram.
Answer:
median 1B: 310
Step-by-step explanation:
3/5n - 4/5 = 1/5n....multiply everything by 5 to get rid of the fractions
3n - 4 = n
-4 = n - 3n
-4 = -2n
-4/-2 = n
2 = n <==