(a) Time taken in walking both the ways = 12 hours 20 minutes ...(i) Time taken in walking one way and riding back= 9 hours 50 minutes ...(ii) By the equation, (ii) × 2 – (i) We get, Time taken by her in riding both ways, ⇒19 hours 40 minutes – 12 hours 20 minutes ⇒ 7 hours 20 minutes