Answer:
B) [tex]10\sqrt{3}[/tex]
Step-by-step explanation:
So basically it's divided into 3 similar triangles and using ratios we can try to find x
long side/short side = long side/short side
(20)/(x) = (x)/(15)
[tex]x^{2}[/tex] = 300
x = [tex]10\sqrt{3}[/tex]
I really hope I didn't make that too complicated-
