Mrs Lee left home at 7 a.m. and drove towards the city. 1²₃ hour later, Mr Lee left the house and drove at an average speed of 103 km/h towards the city. When Mr Lee reached his destination at 1 p.m., Mrs Lee was 27 km away from the city. Find Mrs Lee’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
²₃ h = ²₃ x 60 = 40 min
1²₃ = 1 h 40 min

1 h 40 min after 7 a.m. = 8.40 a.m.

Time that Mr Lee left the house = 8.40 a.m.

Time that Mr Lee took from 8.40 a.m. to 1 p.m. to reach his destination = 4 h 20 min

1 min = ¹₆₀ h
20 min = ²⁰₆₀ h = ¹₃ h
4 h 20 min = 4¹₃ h

Distance that Mr Lee drove
= 4¹₃ x 103
= 446¹₃ km

Distance that Mrs Lee drove when Mr Lee reached
= 446¹₃ - 27 
= 419¹₃ km

Time that Mrs Lee took to travel from 7 a.m. to 1 p.m. = 6 h

Mrs Lee's average speed
= 419¹₃ ÷ 6
= 69⁸₉ km/h

Answer(s): 69⁸₉ km/h