Betty left home at 11.50 a.m. and drove towards the town. 3 hours later, her cousin left their home and drove towards the same town at 89 km/h. When the cousin reached the town at 7.50 p.m., Betty had another 3 km to travel. What was Betty’s average speed? Express your answer in mixed number.
Time that the Betty's cousin started driving = 2.50 p.m.
Duration that Betty's cousin drove from 2.50 p.m. to 7.50 p.m. = 5 h

Distance that Betty's cousin travelled
= 5 x 89
= 445 km

Distance that Betty travelled by the time her cousin reached the city
= 445 - 3
= 442 km

Time that Betty took to travel 442 km = 8 h

Betty's average speed
= 442 ÷ 8
= 55¹₄ km/h

Answer(s): 55¹₄ km/h