I would be very interested in seeing how other people solved this - please post if you used a different route of thinking.D says that k has to be a multiple of 9 K = sum of the digits of M so lets a couple of cases we know m = 18 n when n=0 m=0 so k =0 and k is a multiple of 9 , D is true when n=1,2...6 m= 18, 36,....108 so k = 9 again K is a multiple of 9 , D is again true when n = -1 or -2 or -6 the