In a certain code language,
'A + B' means 'A is the son of B';

'A - B' means 'A is the daughter of B';

'A × B' means 'A is the husband of B' and

'A ÷ B' means 'A is the sister of B'.

Based on the above, how is P related to S if 'P - Q × R ÷ S + T'?

Let's decode the expression 'P - Q × R ÷ S + T' component by component:
P - Q: P is the daughter of Q (P
(−)
is a child of Q).

Q × R: Q is the husband of R (Q
(+)
⇔R
(−)
). This implies R is the mother of P.

R ÷ S: R is the sister of S (R
(−)
and S are siblings sharing the same parents).

S + T: S is the son of T (S
(+)
is a child of T).

Now, let's find how P is related to S:

R is the mother of P.

S is the brother of R (since S is a son, S is male).

Therefore, S is the maternal uncle of P, which means P is S's Sister's daughter (since P is female).