To solve the problem, let's break down the steps Shana needs to follow:

1. Understanding the Problem:

   • Shana has 62 feet of fencing.
   • She decides that the length of the rectangular run will be 20 feet.
   • We need to determine the width of the run.

2. Setting Up the Equation:

   • For a rectangle, the perimeter $P$ is given by: $P = 2 \times \text{Length} + 2 \times \text{Width}$
   • Here, $P = 62$ feet and the length is $20$ feet. Let the width be $w$.

   The equation for the perimeter becomes: $62 = 2 \times 20 + 2 \times w$

3. Solving the Equation:

   • First, simplify the equation: $62 = 40 + 2w$
   • Subtract 40 from both sides to isolate the term with $w$: $22 = 2w$
   • Divide both sides by 2 to solve for $w$: $w = \frac{22}{2} = 11 \text{ feet}$

4. Conclusion:

   • The width of the run is $11$ feet.

Thus, Shana's rectangular dog run will have a length of 20 feet and a width of 11 feet, using all 62 feet of fencing.

Would you like further details or have any questions?

---

Related Questions:

1. What would the dimensions be if Shana decided to maximize the area of the rectangular run?
2. How much area will the dog run enclose with the given dimensions?
3. What if Shana had 80 feet of fencing instead? How would the width change?
4. How would the equation change if the run was a square?
5. What is the difference in area between Shana's rectangular run and a square run using the same 62 feet of fencing?

Tip: When dealing with perimeter problems, remember to distribute the fencing equally among the sides unless there's a specific reason to favor one dimension (like length over width).