Mary left home at 11.30 a.m. and drove towards the campsite. 3 hours later, her uncle left their home and drove towards the same campsite at 84 km/h. When the uncle reached the campsite at 7.30 p.m., Mary had another 2 km to travel. What was Mary’s average speed? Express your answer in mixed number.
Time that the Mary's uncle started driving = 2.30 p.m.
Duration that Mary's uncle drove from 2.30 p.m. to 7.30 p.m. = 5 h

Distance that Mary's uncle travelled
= 5 x 84
= 420 km

Distance that Mary travelled by the time her uncle reached the city
= 420 - 2
= 418 km

Time that Mary took to travel 418 km = 8 h

Mary's average speed
= 418 ÷ 8
= 52¹₄ km/h

Answer(s): 52¹₄ km/h