A conducting sphere of radius R and carrying a charge Q is joined to an uncharged conducting sphere of radius 2R, the charge transferred from one sphere to the other will be...

Hi Cathy

On joining the two spheres their potential will become equal

Let the charge remaining on charged sphere be q then by charge conservation, charge on uncharged sphere will be (Q - q).

Their potential will be equal so,

Kq/R = K(Q-q)/2R

=>  q = Q/3

So charge transferred from initially charged sphere to initially uncharged sphere is Q - Q/3 = 2Q/3