Three formulas now give power: P = IV, P = V²/R, and P = I²R. A problem hands you two quantities. The skill is reading which two you have, and reaching for the formula that uses exactly those two.
Here is one resistor on a test bench, with three versions of the same problem.
Version 1 gives the current through the resistor and the voltage across it. P = IV uses exactly those two. So P = IV finds the power directly.
But version 2 gives the current through the resistor and its resistance. P = IV needs the voltage, which is not given. P = I²R uses exactly those two. So P = I²R finds the power directly.
And version 3 gives the voltage across the resistor and its resistance. P = V²/R uses exactly those two. So P = V²/R finds the power directly.
'Directly' means one formula, one substitution. With the voltage and the resistance, P = IV could still get there, but only after I = V/R finds the current first. Two steps instead of one.
A 30 Ω resistor carries 2.0 A. Which formula gives its power directly?
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Name the given pair first; the formula follows.
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