Chickens and rabbits in the same cage, a total of 100 heads, 272 legs, how many chickens and rabbits each? The reason should be explained clearly

Chickens and rabbits in the same cage, a total of 100 heads, 272 legs, how many chickens and rabbits each? The reason should be explained clearly

Set X chickens, then 100-x rabbits, then
2X+4(100-X)=272
The solution is x = 64
There are 64 chickens and 36 rabbits

Chickens and rabbits in the same cage, a total of 100 heads, 272 legs, number of chickens and rabbits, equation

Suppose there are x chickens, then there are (100-x) rabbits
So 2x + 4 (100-x) = 272
The solution is x = 64
100-64=36
A: there are 64 chickens and 36 rabbits

There are 20 heads and 54 legs in the same cage. How many chickens and rabbits are there?
There is a way of thinking: there are 20 heads, all chickens, and then 20 × 2 = 40 (pieces) 54 legs - 40 legs = 14 legs, and then what to do

If there are x chickens, there are (20-x) rabbits
　　2x+4（20-x）=54
　　80-2x=54
　　2x=26
　　x=13
The number of chickens: x = 13, the number of rabbits: (20-x) = 7
A: there are 13 chickens and 7 rabbits
The problem of chicken and rabbit in the same cage is to select the appropriate unknown quantity to solve the equation of one variable and grasp the conditions provided by the problem
Another way is to set up two unknowns. I don't recommend it. I think the less unknowns, the better=
the end~