Xandra left home at 11.40 a.m. and drove towards the town. 2 hours later, her older brother left their home and drove towards the same town at 99 km/h. When the older brother reached the town at 4.40 p.m., Xandra had another 6 km to travel. What was Xandra’s average speed? Express your answer in mixed number.
Time that the Xandra's older brother started driving = 1.40 p.m.
Duration that Xandra's older brother drove from 1.40 p.m. to 4.40 p.m. = 3 h

Distance that Xandra's older brother travelled
= 3 x 99
= 297 km

Distance that Xandra travelled by the time her older brother reached the city
= 297 - 6
= 291 km

Time that Xandra took to travel 291 km = 5 h

Xandra's average speed
= 291 ÷ 5
= 58¹₅ km/h

Answer(s): 58¹₅ km/h