Chloe has twice as many cats as her sister has dogs. Her brother has two turtles. Together, they have twelve pets. Write an equation that can be used to find how many of each pet they have.

Let's assume that Chloe has "c" cats and her sister has "d" dogs. We are also given that Chloe's brother has two turtles.

The first piece of information tells us that Chloe has twice as many cats as her sister has dogs. Therefore, we can write the equation:

c = 2d

We are also given that together they have twelve pets. This can be represented by the equation:

c + d + 2 = 12

Combining these two equations, we have the system of equations:

c = 2d
c + d + 2 = 12

Let's assign variables to represent the number of each pet.

Let:
- c = number of cats Chloe has
- d = number of dogs Chloe's sister has
- t = number of turtles Chloe's brother has

From the given information, we can create the following equations:

"Chloe has twice as many cats as her sister has dogs":
c = 2d

"Her brother has two turtles":
t = 2

"Together, they have twelve pets":
c + d + t = 12

Therefore, the equation that can be used to find how many of each pet they have is:
2d + d + 2 = 12