Chapter 25 - Capacitance - Problems - Page 740: 15e

$V_2 = 10.0~V$

The total potential difference across the capacitors in any path in the circuit is $20.0~V$ since this is the battery voltage. In part (c), we found that the potential difference across both $C_1$ and $C_6$ is $10.0~V$ Note that there is a path through the circuit across $C_2$ and then $C_1$ Therefore, $V_2 = V - V_1 = 20.0V - 10.0 V = 10.0~V$