represent
r=number of rabbits
c=number of chickens
1 rabbit=4 feet and 1 head
1 chicen=2 feet and 1 head
rabbits head+chicen heads=72
1r+1c=72
feet=200
4 times r+2 times c=200
4r+2c=200
divide both sides by 2
2r+c=100
we have
r+c=72
2r+c=100
make first equation negative and add to second equation
-r-c=-72
2r+c=100 +
1r+0c=28
r=28
subsitute
r+c=72
28+c=72
subtract 28
c=44
44 chickens and 28 rabits
