প্রদত্ত সমীকরণ, $$ \begin{aligned} \frac{0.15 \times 10^p}{0.3 \times 10^q} &= 5 \times 10^7 \\ \Rightarrow \frac{0.15}{0.3} \times 10^{p-q} &= 5 \times 10^7 \\ \Rightarrow 0.5 \times 10^{p-q} &= 5 \times 10^7 \\ \Rightarrow 10^{p-q} &= \frac{5}{0.5} \times 10^7 \\ \Rightarrow 10^{p-q} &= 10 \times 10^7 \\ \Rightarrow 10^{p-q} &= 10^8 \\ \therefore p-q &= 8 \end{aligned} $$ সঠিক উত্তর: 8