Nicole left home at 11.25 a.m. and drove towards the suburb. 2 hours later, her grandmother left their home and drove towards the same suburb at 84 km/h. When the grandmother reached the suburb at 5.25 p.m., Nicole had another 3 km to travel. What was Nicole’s average speed? Express your answer in mixed number.
Time that the Nicole's grandmother started driving = 1.25 p.m.
Duration that Nicole's grandmother drove from 1.25 p.m. to 5.25 p.m. = 4 h

Distance that Nicole's grandmother travelled
= 4 x 84
= 336 km

Distance that Nicole travelled by the time her grandmother reached the city
= 336 - 3
= 333 km

Time that Nicole took to travel 333 km = 6 h

Nicole's average speed
= 333 ÷ 6
= 55¹₂ km/h

Answer(s): 55¹₂ km/h