Answer:
Below
Explanation:
For RIGHT triangles
Cos (21°) = adjacent leg / hypotenuse
cos ( 21°) = x / 21
re-arrange to
21 * cos (21°) = x then use calculator to find x = 19.6 units
( it may not look like it from the picture...but the picture is not drawn to scale : a 21° angle is much smaller than pictured)