Given points $P, Q, R$ in a plane with:
- $P Q=15$
- $Q R=10$

We want to compare:
- Quantity A: distance PR
- Quantity B: 20

By the triangle inequality, the distance between two points $P$ and $R$ satisfies:

$$
\(|P Q-Q R| \leq P R \leq P Q+Q R\)
$$


Substitute the values:

$$
\(\begin{gathered}
|15-10| \leq P R \leq 15+10 \\
5 \leq P R \leq 25
\end{gathered}\)
$$


Thus, $P R$ could be less than, equal to, or greater than 20 depending on the configuration of points $P, Q$, and $R$.

Conclusion:
The relationship between Quantity A and Quantity B cannot be determined from the given information.