To find the perimeter of a rectangle, you can use the formula:

$\text{Perimeter} = 2 \times (\text{length} + \text{width})$

In Thelma's case, the length is 9 meters and the width is 7 meters. Plugging in these values:

$\text{Perimeter} = 2 \times (9\, \text{m} + 7\, \text{m}) = 2 \times 16\, \text{m} = 32\, \text{m}$

So, the perimeter of Thelma's backyard is 32 meters.

Would you like more details or have any questions? Here are some related questions you might find interesting:

1. How would the perimeter change if the length were increased by 2 meters?
2. What is the area of Thelma's backyard?
3. If Thelma adds a fence that costs $5 per meter, what would be the total cost?
4. How does the perimeter of a square compare to that of a rectangle with the same area?
5. If she wants to plant a garden inside the backyard, how would the perimeter affect the layout?

Tip: Always double-check the dimensions before calculating perimeter or area to ensure accuracy.