Answer 1

because // operator is used for floor decision which returns the quotient instead of the reminder.
6 can divide 20 by three times.
20/6 = 3 # remainder is 2 and quotient is 3

https://www.tutorialspoint.com/JUMP_LINK__&&__python__&&__JUMP_LINK/python_basic_operators.htm
https://stackoverflow.com/questions/183853/in-python-2-what-is-the-difference-between-and-when-used-for-division
https://stackoverflow.com/questions/14444520/two-forward-slashes-in-python