We will have the following:
From the graph we will have that:
[tex]<\text{CDF}+<\text{FDE}=90[/tex]
Thus:
[tex](2x)+(x+9)=90\Rightarrow3x+9=90[/tex][tex]\Rightarrow3x=81\Rightarrow x=27[/tex]
Then we will have that the angle FDE is:
[tex]<\text{FDE}=(27)+9\Rightarrow<\text{FDE}=39[/tex]
So, angle FDE is 36°.
