Correct Answer: P ÷ Q – R

Solution : Let's check the given options –
First option: P ÷ Q × R

As per the given information, the family tree will be as follows –

Here, the quadrilateral represents the male, and the circular figure represents the female in the figure. From the above family tree, it is evident that P is the mother of R.
Second option: R – Q ÷ P
As per the given information, the family tree will be as follows –

Here, the quadrilateral represents the male, and the circular figure represents the female in the figure. From the above family tree, it is evident that P is either the grandson or granddaughter of R.
Third option: P ÷ Q – R
As per the given information, the family tree will be as follows –

Here, the quadrilateral represents the male, and the circular figure represents the female in the figure. From the above family tree, it is evident that P is the paternal grandmother of R.
Fourth option: Q ÷ P – R
As per the given information, the family tree will be as follows –

Here, the quadrilateral represents the male, and the circular figure represents the female in the figure. From the above family tree, it is evident that P is the father of R.

So, only the expression in the third option fulfils the relation given in the question. Hence, the third option is correct.