For example, you used the actual rather than the angular frequency to calculate the reactances or you forgot that the current is the impedence divided into the voltage or some other silly thing. And most of you forgot the power factor when computing the average power supplied to the circuit. Recall the power factor is the cosine of the phase angle. Finally, your phasor diagrams sucked . Except some of you apparently forgot what the definition of intensity is.
Intensity is power per unit area.