You cannot divide by zero because zero has no multiplicative inverse: No real number multiplied by zero equals any number other than zero. This is clearer when you realize that any number multiplied by zero must be zero; therefore, you cannot divide by
zero (it is undefined).

You can make any fraction into a whole number by multiplying the fraction by the same number in the denominator. For example, if you multiply 1/3 by 3, you get 1; if you multiply 1/2 by 2, you get 1; if you multiply 2/3 by 3, you would get 2.
I think, though, that what you probably want...