Jean left home at 10.50 a.m. and drove towards the countryside. 3 hours later, her older sister left their home and drove towards the same countryside at 86 km/h. When the older sister reached the countryside at 6.50 p.m., Jean had another 2 km to travel. What was Jean’s average speed? Express your answer in mixed number.
Time that the Jean's older sister started driving = 1.50 p.m.
Duration that Jean's older sister drove from 1.50 p.m. to 6.50 p.m. = 5 h

Distance that Jean's older sister travelled
= 5 x 86
= 430 km

Distance that Jean travelled by the time her older sister reached the city
= 430 - 2
= 428 km

Time that Jean took to travel 428 km = 8 h

Jean's average speed
= 428 ÷ 8
= 53¹₂ km/h

Answer(s): 53¹₂ km/h