Xuan left home at 11.50 a.m. and drove towards the province. 2 hours later, her cousin left their home and drove towards the same province at 90 km/h. When the cousin reached the province at 4.50 p.m., Xuan had another 6 km to travel. What was Xuan’s average speed? Express your answer in mixed number.
Time that the Xuan's cousin started driving = 1.50 p.m.
Duration that Xuan's cousin drove from 1.50 p.m. to 4.50 p.m. = 3 h

Distance that Xuan's cousin travelled
= 3 x 90
= 270 km

Distance that Xuan travelled by the time her cousin reached the city
= 270 - 6
= 264 km

Time that Xuan took to travel 264 km = 5 h

Xuan's average speed
= 264 ÷ 5
= 52⁴₅ km/h

Answer(s): 52⁴₅ km/h