I'm specifically referring to this group of questions here: https://www.cs.rice.edu/~nakhleh/COMP481/final_review_sp06_sol.pdf
So as I've learnt it, say we want to prove a new Language L is undecidable using a known undecidable language D, we use Oracle calls to L to solve an instance of D right?
In none of these questions is an oracle used - For example, with L9 :"M' on input w: it runs M on x and accepts if M halts on x" That's the algorithm; no oracle is used. I understand the reasoning to their solutions, but shouldn't they be using an oracle call? I'm very new to this so sorry if I'm misunderstanding