$PV = nRT$ is one fact wearing four outfits: solve it for $P$, $V$, $n$ or $T$ and it answers four different exam questions. Solved for $n$ it is a gas COUNTER — the stockroom's way of auditing a cylinder without opening it. Solved for $T$ it is a thermometer made of algebra. The ladder is the one you know: rearrange first, sockets second, arithmetic last.

The difference at this rung: the numbers now arrive the way labs actually hand them over. Thermometers read Celsius — YOURS is the job of crossing to kelvin before the socket, and the wrong answers below are exactly what happens when that crossing is skipped. Slow is smooth: write the kelvin figure down before touching anything else, and the rest is bookkeeping.