If X × Y means that X is the mother of Y, X - Y means that X is the father of Y, X ÷ Y means that X is the sister of Y, then which of the following expression shows that P is the maternal grandfather of R?

P - Q × R 

After checking all the options, we get the answer from option (iii):

i) Q × R : Q is mother of R

ii) P - Q : P is father of Q

Relate both equations, we get : P is maternal grandfather of R.