A farmer was counting his chickens and pigs. He had 16 animals in all and counted 54 legs. How many chickens does he have

5 chickens

Step-by-step explanation:

Let's set chickens and pigs with variables "c" and "p" respectively.

We know there a 16 animals in all, so there are:

c+p=16

We know there are 54 legs and chickens have 2 legs and pigs have 4 legs each:

2c+4p=54

Now we have our system of equations:

c+p=16

2c+4p=54

We are trying to find the number of chickens, so we write the first equation in respect to c.

p=16-c

Substituting the first derived equation to equation two:

2c+64-4c=54

Simplifying:

64-2c=54

2c=10

c=5

So there are 5 chickens.