If A + B means A is the sister of B;
A - B means A is the brother of B;
A x B means A is the daughter of B,
Which of the following shows the relation that E is the maternal uncle of D ?

Answer: C. D x F + E

Clearly, E is the maternal uncle of D means D is the daughter of the sister (say F) of E i.e. D x F + E.
Hence the answer is (c).