Answer:
(C)

Explanation:
Given: It is given that OP is parallel to NQ and ON=7, NM=21. PQ=x, QM=36.
To find: The value of x.
Solution: It is given that OP is parallel to NQ and ON=7, NM=21. PQ=x, QM=36, thus using the proportionality theorem, we get

Substituting the given values, we have

Upon solving the above equation, we get




Hence, the value of x is 12 and option C is correct.