<human>:  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?
<bot>: Define a variable ** Let x represent the number of Khaki Campbell ducks.
How many Cayugas are there? ** Cayugas:3+2x
How many Muscovies are there? ** Muscovies:4+(3+2x)=7+2x
Write an equation ** Total: x+3+2x+7+2x=90
Combine like terms ** 5x+10=90
Subtract 10 from both sides ** 5x=80
Divide by 5 ** x=<<16=16>>16
How many Muscovies are there? ** Muscovy: 7+2(16)=39
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