Note that the triangle on the left is a 30-60-90 right triangle
The side opposite the 30° angle = 1
The side opposite the right angle is twice this = 2
And the triangle on the rigth is also 30-60-90
The side opposite the 30° angle = the hypotenuse of the first triangle
"x" is oposite the 60° angle and is √3 times as long as the side opposite the 30° angle
So
"x" = 2√3