Can u please explain how to do these questions

Dear student,
$$\begin{gathered} R=\frac{V^2}{P} \\ \Rightarrow R \alpha \frac{1}{P} \\ \frac{R_{25}}{R_{50}}=\frac{P_{50}}{P_{25}}=\frac{50}{25}=2 \end{gathered}$$

Post other questions in a different thread.

Regards