20.50 * 0.8 = $16.40
16.40 * 0.4 = $6.56
Final selling price = $6.56
Use photomath ! It's an app that gives you the answer with the explanation and it shows you how it got to the answer !
The equation is put in slope intercept form which is y=mx+b
The slope is m and in this case it is -1/2.
To find the y intercept substitute in 0
for x then solve.

Answer:
tan 21 = 17 000 / d
d = 17000/ tan21 = 44286.5 ft