Gwen left home at 10.45 a.m. and drove towards the suburb. 3 hours later, her older brother left their home and drove towards the same suburb at 89 km/h. When the older brother reached the suburb at 6.45 p.m., Gwen had another 5 km to travel. What was Gwen’s average speed? Express your answer in mixed number.
Time that the Gwen's older brother started driving = 1.45 p.m.
Duration that Gwen's older brother drove from 1.45 p.m. to 6.45 p.m. = 5 h

Distance that Gwen's older brother travelled
= 5 x 89
= 445 km

Distance that Gwen travelled by the time her older brother reached the city
= 445 - 5
= 440 km

Time that Gwen took to travel 440 km = 8 h

Gwen's average speed
= 440 ÷ 8
= 55 km/h

Answer(s): 55 km/h