Answer:
21.4
Explanation:
trigonometry.
sine is up or down for an angle in the circle.
cosine is left or right for an angle in the circle.
so, imagine a circle with is center being the corner with the 31 degree angle, and with the radius x.
then
11 = sin(31)×x
=> x = 11/sin(31) = 21.4 (21.35764...)