The division operation is undefined for divisors of exactly zero. Try it on your calculator.

If that doesn't clear it up, Wikipedia ought to: Division by zero.

Consider this unbreakable relationship:

x = a / b
a = b * x
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This relationship is fundamental to algebra; one expression cannot be decoupled from the other. So if x = a / 0, then x * 0 = a. If 'a' is non-zero, there is no value for 'x' that can produce a non-zero 'a' if 'b' is zero. Division by zero is undefined; it has no solution.