So input $$= R(s)$$ and output $$= C(s)$$ and forward transfer $$= G(s)$$ and feedback transfer $$= G_2(s)$$
deriving feedback now $$= G_2(s)C(s)$$ forward signal $$= R(s) - \text{feedback}$$$$ =R(s) - G_2(s)C(s)$$ output $$C(s) = G(s)(R(s) - G_2(s)C(s))$$
Now I don't understand this step The text says next is $$C(s) = \frac{G(s)}{1 + G_2(s)G(s)}R(s)$$