Mrs Yeo left home at 9 a.m. and drove towards the city. 1¹₃ hour later, Mr Yeo left the house and drove at an average speed of 94 km/h towards the city. When Mr Yeo reached his destination at 3 p.m., Mrs Yeo was 12 km away from the city. Find Mrs Yeo’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₃ h = ¹₃ x 60 = 20 min
1¹₃ = 1 h 20 min

1 h 20 min after 9 a.m. = 10.20 a.m.

Time that Mr Yeo left the house = 10.20 a.m.

Time that Mr Yeo took from 10.20 a.m. to 3 p.m. to reach his destination = 4 h 40 min

1 min = ¹₆₀ h
40 min = ⁴⁰₆₀ h = ²₃ h
4 h 40 min = 4²₃ h

Distance that Mr Yeo drove
= 4²₃ x 94
= 438²₃ km

Distance that Mrs Yeo drove when Mr Yeo reached
= 438²₃ - 12 
= 426²₃ km

Time that Mrs Yeo took to travel from 9 a.m. to 3 p.m. = 6 h

Mrs Yeo's average speed
= 426²₃ ÷ 6
= 71¹₉ km/h

Answer(s): 71¹₉ km/h