Closed-Loop Voltage Gain of Circuit Problem
Write a KCL for each of the two nodes on the T-Network, namely \$V_a\$ and \$V_b\$.

Notice that we have:

\$\dfrac{V_{in}}{R}=-\dfrac{V_a}{R}\$

KCL for the two nodes:

\$\dfrac{2V_a}{R}\$ + \$\dfrac{V_a-V_b}{R}\$ = 0  ,

\$\dfrac{V_b}{R}\$ + \$\dfrac{V_b-V_a}{R}\$ + \$\dfrac{V_b-V_o}{R} \$ = 0

Thus,

\$\ 3V_a - V_b = 0 \$

\$\ 3V_b - V_a = V_o \$

Plug em into mathematica and you'll get:

\$\ V_a = \dfrac{V_o}{8}\$

And:

\$\dfrac{V_o}{V_{in}} = -8\$