A farmer has some hens and some goats. If the total number of animal heads is 80 and the total number of animal feet is 200, what is the total number of goats?

Correct Answer: The total number of goats is 20 (Option 3).

Step-by-Step Explanation:
Let us break down the problem step-by-step using algebra.

Step 1: Define the variables
Let $h$ represent the number of hens.
Let $g$ represent the number of goats.

Step 2: Set up equations based on the given information
1. Each hen has 1 head and each goat has 1 head. Since the total number of animal heads is 80, we can write our first equation:

$h+g=80$

2. A hen has 2 feet and a goat has 4 feet. Since the total number of animal feet is 200, we can write our second equation:

$2h+4g=200$

Step 3: Solve the system of equations
From the first equation, we can express $h$ in terms of $g$:

$h=80-g$

Now, substitute this expression for $h$ into the second equation:

$2(80-g)+4g=200$

Expand the equation:

$160-2g+4g=200$

Combine like terms:

$160+2g=200$

Subtract 160 from both sides:

$2g=200-160$

$2g=40$

Divide by 2 to find the number of goats ($g$):

$g=20$

Conclusion:
The total number of goats is 20.