What is the random variable $Z: \Omega \to \mathbb{R}$ by the symbol $Z= X/Y$?

Question

In my lecture note, a real-valued random variable is defined as follows:

Then I have an exercise:

Actually, my lecture notes do not have a definition of a random variable generated by other ones.

We already have funtions $X : \Omega \to \mathbb{R}$ and $Y : \Omega \to \mathbb{R}$.

My question: What is the random variable $Z: \Omega \to \mathbb{R}$ by the symbol $Z= X/Y$? I mean, for each $\omega \in \Omega$, what is $Z(\omega)$?

Thank you so much for your help!