Answer
2.3 diopters
Work Step by Step
The person’s current near point is 52 cm. With the reading glasses, an object placed 25 cm from the face (23 cm from the lens) should produce a virtual image that is 52 cm from the eye (50 cm from the lens).
In other words, $d_o=0.23 m$ and $ d_i=-0.50 m $. Find the power of the lens from the lens equation.
$$P=\frac{1}{f}=\frac{1}{d_o}+\frac{1}{d_i}$$
$$P=\frac{1}{0.23m}+\frac{1}{-0.50m}=2.3D$$