LET X=O implies Y+Z=20 Y=0 implies Z=20 Y=1 IMPLIES Z=19 AND SO ON.... NO OF SOLN'S FOR X=0 ARE 21 X=1 implies Y+Z=16 Y=1 implies Z=15 AND SO ON.... NO OF SOLN'S FOR X=1 ARE 17 SO ON................. THUS THE ANS IS 21+17+13+9+5+1=66