To find R, we can rearrange the equation \( T = \frac{D}{R} \) to solve for R:
\[ R = \frac{D}{T} \]
Now, plug in the values for D and T:
\[ D = 75 \quad \text{and} \quad T = 25 \]
Substituting these values into the equation gives:
\[ R = \frac{75}{25} \]
Calculating this:
\[ R = 3 \]
Therefore, R is equal to 3. The correct answer is B. 3.