Xuan left home at 11.10 a.m. and drove towards the city. 2 hours later, her older brother left their home and drove towards the same city at 89 km/h. When the older brother reached the city at 4.10 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 older brother started driving = 1.10 p.m.
Duration that Xuan's older brother drove from 1.10 p.m. to 4.10 p.m. = 3 h

Distance that Xuan's older brother travelled
= 3 x 89
= 267 km

Distance that Xuan travelled by the time her older brother reached the city
= 267 - 4
= 263 km

Time that Xuan took to travel 263 km = 5 h

Xuan's average speed
= 263 ÷ 5
= 52³₅ km/h

Answer(s): 52³₅ km/h