Answer
79$\frac{1}{2}$ in
Work Step by Step
three vents are equally spaced along a wall 26 ft 6 in. = 26 x 12 + 6 = 318 in.
So it divides the walls into four equal dimesions
Dimension of d = $\frac{318}{4}$ = $\frac{159}{2}$
= 79$\frac{1}{2}$ in
