Let the distance between A and B is x km.
Time taken by father to cover x km at a speed of 12 Km/hr = \( \Large \frac{x}{12}hours\)
And time taken by son to over x km at a speed of 18 Km/hr = \( \Large \frac{x}{18} hours\)
According to question,
= \( \Large \frac{x}{12} - \frac{x}{18} = \frac{60 + 60}{60}\)
= > \( \Large \frac{3x - 2x}{36} = 2\)
= > \( x = 2 \times 36 \)
= 72 km