Answer:
27.5
Explanation:
With a given angle of 54 deg and the side lengths we have to work with, a and 20 (a is the measure we want to find and 20 is given), we can use the tangent ratio to solve for the side length, since we're dealing with the opposite side length (a) and the adjacent side length (20) relative to the 54 deg angle.
So, tan 54 deg = a/20 (definition of tangent)
Multiply both sides by 20 -> 20*tan 54 deg = a
Input 20*tan 54 deg into a calculator, and you get approx. 27.5