Step-by-step explanation:
let x be the missing side length.We know that hypotenuse is 2x because x is opposite the 30 angle.
Using pythagorean theorem we have that x^2+9^2=(2x)^2
81=4x^2-x^2
81=3x^2
x^2=81/3=27
x=√27
so the missing side is √27
