You cannot divide by zero — not because of a rule, but because it breaks reality.

Teachers say "it's undefined" and move on. Here's why: division asks "how many times does X fit into Y?" How many times does 0 fit into 5? You could add zeros forever and never reach 5. There's no answer — not even infinity, because 0 × ∞ is still indeterminate. Allowing it would mean 1 = 2, and every equation in existence collapses.