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

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

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

Time that Shiyun took to travel 426 km = 8 h

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

Answer(s): 53¹₄ km/h