The image shows a mathematical equation involving $R_2$. I will transcribe it and help solve it step by step.

From the image, the equation seems to resemble this structure:

$\frac{1}{R_2} = \frac{1}{R_1} + \frac{1}{R}$

Let me know if this transcription matches the equation. If so, I can solve for $R_2$. Otherwise, please clarify further.