Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
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?

### Response:
Let's represent the number of Muscovies with x, the number of Cayugas with y and the number of Khaki Campbells with z.
We know that there are 4 more Muscovies than Cayugas, so x = y + 4.
We also know that there are 3 more Cayugas than twice as many Khaki Campbells, so y = 2z + 3.
We know that there are 90 ducks total, so x + y + z = 90.
We can substitute x = y + 4 and y = 2z + 3 into the equation x + y + z = 90.
The equation would look like this: (y + 4) + (2z + 3) + z = 90.
We can simplify the equation to 3z + 8 = 90.
We can subtract 8 from both sides of the equation to get 3z = 82.
And we can divide both sides of the equation by 3 to get z = 27.
We can substitute z = 27 into the equation y = 2z + 3 to get y = 2 * 27 + 3 = 57.
We can substitute y = 57 into the equation x = y + 4 to get