>>13616861Finding an LCM is hardly a difficult task but out of a and b it's seriously b that you're struggling with? I assume this is a troll but I'll indulge you anyway.
LCM of 4, 5 and 12 is 60. 60 hours is 2 days and 12 hours which makes things even easier. Two days after Monday is Wednesday and 12 hours means it's the same hour just PM. a) 60 b) 6:00pm Wednesday.