Xuan left home at 10.30 a.m. and drove towards the seaside resort. 3 hours later, her father left their home and drove towards the same seaside resort at 86 km/h. When the father reached the seaside resort at 6.30 p.m., Xuan had another 4 km to travel. What was Xuan’s average speed? Express your answer in mixed number.
Time that the Xuan's father started driving = 1.30 p.m.
Duration that Xuan's father drove from 1.30 p.m. to 6.30 p.m. = 5 h

Distance that Xuan's father travelled
= 5 x 86
= 430 km

Distance that Xuan travelled by the time her father reached the city
= 430 - 4
= 426 km

Time that Xuan took to travel 426 km = 8 h

Xuan's average speed
= 426 ÷ 8
= 53¹₄ km/h

Answer(s): 53¹₄ km/h