Let the distance (home to the railway station), be $D$ km.
We know that, $\text{Time} = \dfrac{\text{Distance}}{\text{Speed}}$
According to the question, $\frac{D}{12} – \frac{D}{15} = \frac{20}{60}$
$\Rightarrow \frac{5D – 4D}{60} = \frac{20}{60}$
$\Rightarrow D = 20$ km
$\therefore$ Distance from home to the railway station $= 20$ km.
Correct Answer $:\text{D}$