You can cancel anything!
In the white-hot forge of test anxiety, a math student hammered out an eldritch weapon with which to reduce a fearful fraction to its lowest form. Dangling by one hand from the precarious perch of a perilous vinculum, our hero gave a mighty swing and smartly smote the object of his dread with the sharp edge of his wicked blade. A mighty explosion!
When the debris cleared, a pair of h's had vanished, cancelled from both numerator and denominator of the deadly fraction. Unfortunately, our hapless hero was not rewarded with success. The poor student, in an excess of zeal, had cancelled That Which Cannot Be Cancelled.
I have seldom seen its like, although cancellation is often misused by math students eager to reduce anything they can. In this instance, our hero left a dangling exponent in the numerator. He decided that the superscript 2 was inherited by the coefficient 4, which directly became 16. Problem solved!
Oh, dear. At least he distributed the cancellation to the other two terms in the numerator—correctly, too. Perhaps there's hope.