To solve for the length of \( d \) using the given dimensions, we can use the Pythagorean theorem, assuming \( d \) represents the diagonal distance across a rectangular prism.
It seems that you might have a right triangle formed by \( w \), \( h \), and \( d \) as the hypotenuse. If this is the case, the equation can be set up as follows:
\[ d = \sqrt{w^2 + h^2} \]
Substituting the known values (where \( w = 20 \) in. and \( h = 18 \) in.):
\[ d = \sqrt{(20)^2 + (18)^2} \]
Calculating the squares:
\[ d = \sqrt{400 + 324} \] \[ d = \sqrt{724} \]
Now, we calculate the square root of 724:
\[ d \approx 26.9 \text{ in.} \]
So, rounding to the nearest tenth, the length of \( d \) is approximately 26.9 in.