Remember that division by zero does not exist.  Just as addition undoes subtraction, multiplication undoes division. 

For example..  5 + 2 = 7. To undo the addition of 2 to 5, subtract 2 from 7.    7 - 2  = 5

8 - 5 = 3.  To undo the subtraction, add 5 to 3 to get  3 + 5 = 8

Now try multiplication to undo division.   6 divided by 3 = 2.  To undo, multiply 2 and 3 to get 6.

This works, but in the next example, it will not.

4 times 0 = 0. If you follow what was done in the examples above, 0 divided by 0 should equal 4, but that is obviously not true.