Xuan left home at 11.30 a.m. and drove towards the countryside. 2 hours later, her auntie left their home and drove towards the same countryside at 76 km/h. When the auntie reached the countryside at 5.30 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 auntie started driving = 1.30 p.m.
Duration that Xuan's auntie drove from 1.30 p.m. to 5.30 p.m. = 4 h

Distance that Xuan's auntie travelled
= 4 x 76
= 304 km

Distance that Xuan travelled by the time her auntie reached the city
= 304 - 4
= 300 km

Time that Xuan took to travel 300 km = 6 h

Xuan's average speed
= 300 ÷ 6
= 50 km/h

Answer(s): 50 km/h