so $n_{1}=\frac{v}{\lambda_{1}}=\frac{v}{4 \times 37.5}$

For tuning fork $'B'$ $\frac{\lambda_{2}}{4}=38.5$

$\therefore n_{2}=\frac{v}{\lambda_{2}}=\frac{v}{4 \times 38.5}$

$\therefore n_{1}-n_{2}=8 \Rightarrow \frac{v}{4 \times 37.5}-\frac{v}{4 \times 38.5}=8$

$\therefore v=(8 \times 4 \times 37.5 \times 38.5)$

$n_{1}=\frac{8 \times 4 \times 37.5 \times 38.5}{4 \times 37.5}=308 \mathrm{\,Hz}$

and $n_{2}=308-8=300 \mathrm{\,Hz}$