help answer please!!

Answer:
h = 19.7 ft.
Step-by-step explanation:
Use the Pythagoras Theorem
[tex](Hypotenuse)^2 = (Base)^2 + (Perpendicular)^2\\\\(20)^2=(3.5)^2+(h)^2\\400=12.25+h^2\\400-12.25=h^2\\387.75=h^2\\[/tex]
Now we take square root on both sides,
[tex]\sqrt{387.75} =\sqrt{h^2}\\19.69=h\\h=19.7\ ft\\[/tex]
so the value of h equals 19.7 ft.