This problem involves finding the length of the diagonal of a rectangular frame. To solve it, we can use the Pythagorean theorem, which is expressed as:

$d = \sqrt{l^2 + w^2}$

Where:

• $d$ is the diagonal,
• $l$ is the length of the rectangle (15 inches),
• $w$ is the width of the rectangle (8 inches).

Let's plug in the values:

$d = \sqrt{15^2 + 8^2} = \sqrt{225 + 64} = \sqrt{289} = 17 \text{ inches}$

Thus, the length of the diagonal is 17 inches.

Would you like further details or have any questions?

Here are 5 related questions for practice:

1. How would the diagonal change if the width were doubled?
2. What is the area of Frank's rectangular frame?
3. How do you apply the Pythagorean theorem to triangles?
4. If the length and width of a frame are the same, how would you calculate the diagonal?
5. Can you find the perimeter of Frank's frame with the given dimensions?

Tip: Whenever you are dealing with right-angled triangles, the Pythagorean theorem is the best tool to find missing sides!