Answer
The potential difference across resistance 5 is $~~7.50~V$
Work Step by Step
The equivalent resistance of $R_4$ and $R_5$ in series is $8.00~\Omega$
The current through $R_4$ and $R_5$ is $i = \frac{12.0~V}{8.00~\Omega} = 1.50~A$
We can find the potential difference across $R_5$:
$\Delta V = (1.50~A)(5.00~\Omega) = 7.50~V$
The potential difference across resistance 5 is $~~7.50~V$
