A + B means, A is the sister of B

A - B means, A is the daughter of B

A×B means, A is the brother of B

A÷B means, A is the husband of B

If X + Y × Z - P ÷ Q + R × S, then how is R related to X?

Maternal Uncle

Note:

↑ or ↓ ⇒ Upward or downward line shown "generation gap" .

   =    ⇒ Double lines shown "relation b/w Husband & Wife"

   —   ⇒ single line shown "relation between them other than Husband & Wife".

So, clearly (b) is correct.