Joelle left home at 11.25 a.m. and drove towards the city. 2 hours later, her uncle left their home and drove towards the same city at 99 km/h. When the uncle reached the city at 4.25 p.m., Joelle had another 6 km to travel. What was Joelle’s average speed? Express your answer in mixed number.
Time that the Joelle's uncle started driving = 1.25 p.m.
Duration that Joelle's uncle drove from 1.25 p.m. to 4.25 p.m. = 3 h

Distance that Joelle's uncle travelled
= 3 x 99
= 297 km

Distance that Joelle travelled by the time her uncle reached the city
= 297 - 6
= 291 km

Time that Joelle took to travel 291 km = 5 h

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

Answer(s): 58¹₅ km/h