Vanessa left home at 10.25 a.m. and drove towards the campsite. 3 hours later, her grandfather left their home and drove towards the same campsite at 90 km/h. When the grandfather reached the campsite at 5.25 p.m., Vanessa had another 3 km to travel. What was Vanessa’s average speed? Express your answer in mixed number.
Time that the Vanessa's grandfather started driving = 1.25 p.m.
Duration that Vanessa's grandfather drove from 1.25 p.m. to 5.25 p.m. = 4 h

Distance that Vanessa's grandfather travelled
= 4 x 90
= 360 km

Distance that Vanessa travelled by the time her grandfather reached the city
= 360 - 3
= 357 km

Time that Vanessa took to travel 357 km = 7 h

Vanessa's average speed
= 357 ÷ 7
= 51 km/h

Answer(s): 51 km/h