Omigosh i put it in the calculator and it said infinity!
Some math nerd named Mr. Multiplication made it up so kids at school would suffer
It was invented by the Babylonians thousands of years ago
There is none you just type it in the box
I said IF YOUR REFFERING TO THAT VIDEO 21!!! But otherwise i say 19
multiply it by 0.5 or divide it by 2
I hope this helped... sorry i couldn't go in depth