Comment
Set up a proportion
12/14 = x/21
They have already won 12 out of 14 games.
What you are asking is how many will the win (call that number x) if they play 21 games.
Solution
12/14 = x/21 Cross multiply
14* x = 12*21 Combine the right
14x = 252 Divide both sides by 14
14x/14 = 252/14 Do the division
x = 18
They should win 18 games.
