In a certain code language:
* '$A+B$ ' means 'A is the wife of B's brother',
* '$A-B$ ' means 'A is the sister of B',
* '$A\times B$ ' means 'A is the wife of B',
* '$A÷B$ ' means 'A is the daughter of B'.

Based on the above, if the expression is '$G+K-L÷M\times Q$ ', how is G related to Q?

Let's decode the expression from right to left step-by-step:
1. $M\times Q\to$ M is the wife of Q. (Q is the husband, M is the wife).
2. $L÷M\to$ L is the daughter of M. Since M is married to Q, L is also the daughter of Q.
3. $K-L\to$ K is the sister of L. This means K is also the daughter of Q and M.
4. $G+K\to$ G is the wife of K's brother.

Since K is the daughter of Q, K's brother is Q's son. G is married to K's brother, which means G is the wife of Q's son.
Therefore, G is the daughter-in-law of Q.