There are 13 animals in the barn. some are chickens and some are pigs. there are 40 legs in all. how many of each animal are there?

Let p = pigs

and c = chickens

p + c = 13 (this is the total number of animals in the barn)

chicken have 2 legs and pigs have 4 legs

2c + 4p = 40 (this is the equation for the total number of legs)

now lets solve for one variable using the first equation

p+c = 13

p = 13 - c

now lets plug that in the 2nd equation

2c+4p = 40

2c + 4 (13-c) = 40

2c + 52 - 4c = 40

now we reduce

-2c = - 12

c = 6

so there are 6 chickens now lets find how many pigs there are by plugging into our first equation

p+6 = 13

p = 7

so there are 6 chickens and 7 pigs

C=chicken

p=pigs

c+p=13~p=13-c (plug in)

2c+4p=40

2c+4 (13-c) = 40

2c+52-4c=40

-2c=-12

c=6

6+p=13

p=7

6 chickens

7 pigs