To solve the problem, we start by noting that a square chicken coop has four equal sides. Let's define \( x \) as the length of each side of the square coop in yards.
The perimeter \( P \) of a square is given by the formula: \[ P = 4x \]
According to the problem, Tin uses 20 yards of fencing for the walls. Therefore, we can set the equation as follows: \[ 4x = 20 \]
To solve for \( x \), we divide both sides of the equation by 4: \[ x = \frac{20}{4} \] \[ x = 5 \]
Thus, the length of each wall of the square coop is \( 5 \) yards.
In summary:
- The equation representing the problem is \( 4x = 20 \).
- The solution is \( x = 5 \) yards.