If we treat the words as variables where M+Y+T=4, then T-Y-M is not necessarily 0 unless specific values are assigned. However, in many logic puzzles of this type, the words represent their lengths or specific values. If M+Y+T=4, then T-Y-M = 0 is only true if Y+M = T (meaning T=2, and Y+M=2). Without a defined key, this is a logic leap, but 0 is the intended 'riddle' answer.