There are chicken and rabbits on a farm. You count 98 legs and your friend counts 30 heads. How many chickens and how many rabbits are there?

Chickens have 1 head and 2 legs

rabbits had 1 head and 4 legs

total heads is 30

c+r=30

total legs is 98

2c+4r=98

divide by 2

c+2r=49

multiply top equation by - 1 and add to 2nd equation

-c-r=-30

c+2r=49 +

0c+1r=19

r=19

sub back

c+r=30

c+19=30

minus 19

c=11

11 chickens

19 rabbits