Explanation:
the Hypotenuse (the inclined length of the staircase) of the right-angled triangle is the radius of an imaginary circle with the center at the vertex with the 64°.
then
11 = cos(64) × r
r = 11/cos(64) = 25.09289236...
and
x = sin(64) × r = sin(64) × 11/cos(64) = 11 × tan(64) =
= 22.55334226... ≈ 22.55