Shannon left home at 10.50 a.m. and drove towards the countryside. 3 hours later, her younger sister left their home and drove towards the same countryside at 97 km/h. When the younger sister reached the countryside at 5.50 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 younger sister started driving = 1.50 p.m.
Duration that Shannon's younger sister drove from 1.50 p.m. to 5.50 p.m. = 4 h

Distance that Shannon's younger sister travelled
= 4 x 97
= 388 km

Distance that Shannon travelled by the time her younger sister reached the city
= 388 - 3
= 385 km

Time that Shannon took to travel 385 km = 7 h

Shannon's average speed
= 385 ÷ 7
= 55 km/h

Answer(s): 55 km/h