Shannon left home at 10.50 a.m. and drove towards the town. 3 hours later, her older brother left their home and drove towards the same town at 83 km/h. When the older brother reached the town at 6.50 p.m., Shannon had another 3 km to travel. What was Shannon’s average speed? Express your answer in mixed number.
Time that the Shannon's older brother started driving = 1.50 p.m.
Duration that Shannon's older brother drove from 1.50 p.m. to 6.50 p.m. = 5 h

Distance that Shannon's older brother travelled
= 5 x 83
= 415 km

Distance that Shannon travelled by the time her older brother reached the city
= 415 - 3
= 412 km

Time that Shannon took to travel 412 km = 8 h

Shannon's average speed
= 412 ÷ 8
= 51¹₂ km/h

Answer(s): 51¹₂ km/h