Answer
(a) nearsighted
(b) diverging
(c) $-3.34~diopters $
Work Step by Step
(a) We know that a nearsighted person with totally relaxed eyes focuses only out a finite distanced from the eye. Hence, the aunt is nearsighted.
(b) We know that the diverging lens can produce an image of a distant object at your aunt's far point distance, and hence the aunt should wear glasses with diverging lenses.
(c) We know that
$ d_{\circ}=25-2cm=23cm $
The far point distance from the glasses is:
$ F=15-2cm=13cm $
Now $\frac{1}{f}=\frac{1}{d_{\circ}}+\frac{1}{d_i}$
$\implies \frac{1}{f}=\frac{1}{23cm}+\frac{1}{-13cm}$
Now power $ P=\frac{1}{f(in \space meters)}$
$ P=\frac{100}{23}-\frac{100}{13}$
$ P=-3.34~diopters $
