Question

my uncle John has a farm.In his farm he has cows and chicken.he doesn't know how many cows and chicken he has .He dose know that he has 36 heads and 104 legs on the cows and chicken.how many of the animals are chicken and cows

Answer 1

X+y=36
4x+2y=104
Then
X=16, y=20. 16 cows and 20 chicken.

Or
104 legs minus 2 times 36 heads and then divided by 2 is the number of cows. (From all legs minus all legs for chicken and 2 legs of each cow. The result is 2 legs per cow. So divided by 2 is the number of cows).
X=(104-2*36)/2=16
Y=36-16=20