I have a conceptual doubt in this question.
If the inner shell is neutral then how can charge flow from the inner shell to the earth(if there is no charge on the inner shell)?
Neutral implied presence of equal positive and negative charge and it does not mean that no proton or electron is present. Hence movement of electron either in or out of the conductor will lead to accumulation of positive or negative charge. Here potential of inner shell initially would be +kq/3r but because of being grounded it's potential should become 0 abd hence charge in form of electrons will flow from ground to shell having value -q/3.