If a rooster laid 13 eggs, and the farmer took 8 of them, and then another rooster laid 12 eggs and 4 of them were rotten, how many of the eggs were left?
I don't know if this is a trick question, because hens lay eggs, not roosters. If not, then the answer is 13. Because 13-8=5, and 5+12=17, finally 17-4=13.