If you divide 100 by 10, you can subtract 10 ten times and then the number becomes 0: 100/10 = 10
30/5 = can subtract 5 six times before the number becomes 0 = 6
Of course, this way you can only do integer division:
33/5: you can subtract 5 six times. The reduced value will then be three, that is - smaller than the value you are dividing by. So the result would be 6. The remaining value is three: that is the modulus (33%5 = 3).
You don't know how many times you can subtract, this is what you have to find out.