Counting to 21 Strategy You need to get them to say 19 or 20; therefore, if you say 18, you win. To say 18, you need to get them to say 16, or 17, so if you say 15, you win. Continuing on, if you say 12 you win. if you say 9, you win, if you say 6, you win, if you say 3, you win. More items... Feb 13, 2017