Answer :
let time traveled pushing motorcycle = t
distance traveled pushing motorcycle = distance traveled on motorcycle
⇒ 3 * t = 60 * (21-t)
⇒ 3t = 1260 - 60t
⇒ 63t = 1260
⇒ t = 1260/63
⇒ t = 20 hours
He pushed the motorcycle for 20 hours
distance traveled pushing motorcycle = distance traveled on motorcycle
⇒ 3 * t = 60 * (21-t)
⇒ 3t = 1260 - 60t
⇒ 63t = 1260
⇒ t = 1260/63
⇒ t = 20 hours
He pushed the motorcycle for 20 hours