Um ... In other words, this problem is simply the solution of our equation. . . But in the third grade, I haven't learned the equation. . .

But in the third grade, the requirements for proof questions are not high.

Number of yellow chickens = 18.

Number of white chickens =2× 18 (the number of white chickens is twice that of yellow chickens) = 18+ 18 (yellow chickens are less than white chickens 18)= 36.

Number of black chickens = 18- 13 (yellow chickens are more than black chickens 13)= 5.

For simplicity, you can write like this:

Yellow chicken = 18.

White chicken =2× 18=36.

Black chicken = 18- 13=5.

A: Yellow chickens 18, 36 white chickens and 5 black chickens.

I will tell you the formula of the equation along the table. I will learn this later, so I don't need to go to the third grade.

Let the yellow chicken be X.

x+ 18=2x

x= 18

2× 18=36.

18- 13=5 pieces.

A: Yellow chickens 18, 36 white chickens and 5 black chickens.