Calculating $E_b/N_0$ from given SNR ratio
HINT:
$$
\frac{S}{N}=\frac{E_b \cdot R_b}{N_0 \cdot B }
$$
With all units linear:
$$\implies \frac{E_b}{N_0} = \frac SN\cdot \frac BR_b\tag{linear}
$$
Now with $S/N$ in $[\rm dB]$ and $R_b$ and $B$ linear, you get $E_b/N_0$ in $[\rm dB]$ as follows:
$$\implies \frac{E_b}{N_0} = \frac SN +10\log_{10}\left(\frac BR_b\right)\tag{in [dB]}$$