Xandra left home at 10.15 a.m. and drove towards the city. 3 hours later, her mother left their home and drove towards the same city at 85 km/h. When the mother reached the city at 6.15 p.m., Xandra had another 5 km to travel. What was Xandra’s average speed? Express your answer in mixed number.
Time that the Xandra's mother started driving = 1.15 p.m.
Duration that Xandra's mother drove from 1.15 p.m. to 6.15 p.m. = 5 h

Distance that Xandra's mother travelled
= 5 x 85
= 425 km

Distance that Xandra travelled by the time her mother reached the city
= 425 - 5
= 420 km

Time that Xandra took to travel 420 km = 8 h

Xandra's average speed
= 420 ÷ 8
= 52¹₂ km/h

Answer(s): 52¹₂ km/h