There are 4 more Muscovy ducks than Cayugas, and 3 more than twice as many Cayugas as Khaki Campbells. If there are 90 ducks total, how many Muscovies are there? Let's answer step by step:
Let x represent the number of Khaki Campbell ducks. Cayugas:3 + 2x. Muscovies:4 + (3 + 2x) = 7 + 2x. Total: x + 3 + 2x + 7 + 2x = 90. 5x + 10 = 90. 5x = 80. x = 16. Muscovy: 7 + 2(16) = 39. The answer: 39.