Linda left home at 11.45 a.m. and drove towards the countryside. 3 hours later, her older sister left their home and drove towards the same countryside at 91 km/h. When the older sister reached the countryside at 7.45 p.m., Linda had another 3 km to travel. What was Linda’s average speed? Express your answer in mixed number.
Time that the Linda's older sister started driving = 2.45 p.m.
Duration that Linda's older sister drove from 2.45 p.m. to 7.45 p.m. = 5 h

Distance that Linda's older sister travelled
= 5 x 91
= 455 km

Distance that Linda travelled by the time her older sister reached the city
= 455 - 3
= 452 km

Time that Linda took to travel 452 km = 8 h

Linda's average speed
= 452 ÷ 8
= 56¹₂ km/h

Answer(s): 56¹₂ km/h