Elyse left home at 11.30 a.m. and drove towards the countryside. 2 hours later, her younger brother left their home and drove towards the same countryside at 86 km/h. When the younger brother reached the countryside at 5.30 p.m., Elyse had another 2 km to travel. What was Elyse’s average speed? Express your answer in mixed number.
Time that the Elyse's younger brother started driving = 1.30 p.m.
Duration that Elyse's younger brother drove from 1.30 p.m. to 5.30 p.m. = 4 h

Distance that Elyse's younger brother travelled
= 4 x 86
= 344 km

Distance that Elyse travelled by the time her younger brother reached the city
= 344 - 2
= 342 km

Time that Elyse took to travel 342 km = 6 h

Elyse's average speed
= 342 ÷ 6
= 57 km/h

Answer(s): 57 km/h