Among them, one digit is 5, 7 and 9.
These two figures are 57, 59, 75, 79, 95 and 97.
These three numbers are 579, 597, 759, 795, 957 and 975.
2. A * * * can form 10 natural numbers.
Among them: a number has 4 and 6.
These two numbers are 40, 46, 60 and 64.
These three numbers are 406, 460, 640 and 604.
3. If there are x chickens, there are 12-X rabbits;
Because a chicken has two legs and a rabbit has four.
Column 2X+4( 12-X)=30.
Found that X=9
12-9=3
The Zhang family has 9 chickens and 3 rabbits.