ClearAll[Fairshare]
Fairshare[n_List, b_Integer : 2] := Fairshare[#, b] & /@ n
Fairshare[n_Integer, b_Integer : 2] := Mod[Total[IntegerDigits[n, b]], b]
Fairshare[Range[0, 24], 2]
Fairshare[Range[0, 24], 3]
Fairshare[Range[0, 24], 5]
Fairshare[Range[0, 24], 11]