In a certain code language,
'P∗Q' means 'P is the father of Q',
'P#Q' means 'P is the sister of Q',
'P+Q' means 'P is the brother of Q',
'P=Q' means 'P is the mother of Q',
'P−Q' means 'P is the son of Q'.

Based on the above, how is P related to R if 'P∗Q=R'?

Let's decode the given coded relational expression step-by-step:
P∗Q=R
Q=R: This means Q is the mother of R. (Q is Female)

P∗Q: This means P is the father of Q. (P is Male)

Now, putting it together:

Q is the mother of R.

P is the father of Q.

Therefore, P is the father of R's mother, which means P is the Mother's father (Maternal Grandfather) of R.