Question 822133
I suppose we can assume that there are no tie games.
Set w = games won
    l = games lost
 w + l = 57
    l = w + 21
 Substitute ( w + 21 ) for l  in w + l = 57
    w + ( w + 21 ) = 57
    2w + 21 = 57
subtract 21 from each side
    2w = 36
    w = 18
substitute 18 for w in  l = w + 21
    l = 18 + 21
    l = 39