Look at drawing and say is it right or not.

First of all. The bigger circle on the drawing is a cylinder. Three smaller circles are spheres. And they are situated as you can see on the drawing.

I must find radius of cylinder (r). R is radius of the sphere. So my solution is the following:

H=R*sqrt(3)

X=H-R => R*sqrt(3)-R => R*[sqrt(3)-1]

r=(2*H)+X => 2*[R*sqrt(3)]+X => 2*[R*sqrt(3)]+R*[sqrt(3)-1] => R*[3*sqrt(3)-1]