Purchases or payable t account

Sir in F3 BPP kit there are two questions in chapter incomplete records both asking for purchases to be found out through T account but in the answer sheet I was a bit confused.

In the first question the examiner found purchases through payable T account and in the other question he found the answer by making purchase t account.

So how can we decide that which Y account to make to find out a particular missing value bcoz examiner is finding purchases through making two different t accounts.

For reference question number is 20.4 and 20.10.