Hi there! Thanks for your questions ;)
The answers are quite easily, go through the steps below so that you can catch it up yourself!!
a)
= [tex]\rm{sin (x) = \dfrac{9}{20}}[/tex]
= [tex]\rm{0.45}[/tex]
= [tex]\rm{x = arcsin(0.45)}[/tex]
= [tex]\rm{26.74 \: degrees}[/tex]
(b)
= [tex]\rm{h = 20 \times cos(x)}[/tex]
= [tex]\rm{20 \times cos(26.74)}[/tex]
= [tex]\rm{ 17.86 \: m}[/tex]
Hope it is helpful!
