Three entries, then a trial balance that will not tie
The first three questions are transactions you have lived through: rent paid, a customer who has not paid yet, a machine repaired. Pick the entry that records each one properly. Then come two trial balances, each with exactly one error planted in it, and the totals refusing to agree.
Finding that error is not a matter of staring harder. It is arithmetic, and it obeys rules. An amount put on the wrong side does not vanish — it moves, so the books are out by twice it. A balance left out altogether is out by exactly once. And two digits swapped by a tired finger produce a difference that is always divisible by nine. Divide the gap by nine before you touch the ledger; if it goes cleanly, you have narrowed the search to a single kind of mistake in about three seconds.
Why this one cannot go out of date
Not a single question here rests on a rate, a threshold, a section or a due date. Double entry has not changed since 1494 and is not about to, and the trial balances are generated with the error planted and the gap computed — so the answer is arithmetic, not something anybody typed in and hoped stayed true.
This is bookkeeping practice, not advice on your own books. If something in your trial balance genuinely will not tie, the fix is a ledger and a professional, not a puzzle.