Let the skiers be K. Let the snowboarders be N
Therefore K:N = 1:2
If 1250 more snowboarders bought than skiers.
If K are the skiers, therefore the snowboarders , N = K + 1250
K:N = 1:2 : K:(K + 1250) = 1:2
K/(K+1250) = 1/2
2K = 1*(K+1250)
2K = 1*(K+1250)
2K = K + 1250
2K - K = 1250
K = 1250
1250 skiers bought the season passes.