(54-20×2)÷(4-2),

= 14÷2,

=7 (only),

Then the chicken has: 20-7= 13 (only);

Answer: There are 13 chickens and 7 rabbits.

Method 2: suppose there are x rabbits and 20-x chickens, and the equation can be obtained according to the meaning of the question: 4.

4x+2(20-x)=54，

4x+40-2x=54，

2x= 14，

x=7，

20-7= 13 (only),

Answer: There are 13 chickens and 7 rabbits.