Mrs Kok left home at 8 a.m. and drove towards the city. 1¹₄ hour later, Mr Kok left the house and drove at an average speed of 107 km/h towards the city. When Mr Kok reached his destination at 2 p.m., Mrs Kok was 18 km away from the city. Find Mrs Kok’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₄ h = ¹₄ x 60 = 15 min
1¹₄ = 1 h 15 min

1 h 15 min after 8 a.m. = 9.15 a.m.

Time that Mr Kok left the house = 9.15 a.m.

Time that Mr Kok took from 9.15 a.m. to 2 p.m. to reach his destination = 4 h 45 min

1 min = ¹₆₀ h
45 min = ⁴⁵₆₀ h = ³₄ h
4 h 45 min = 4³₄ h

Distance that Mr Kok drove
= 4³₄ x 107
= 508¹₄ km

Distance that Mrs Kok drove when Mr Kok reached
= 508¹₄ - 18 
= 490¹₄ km

Time that Mrs Kok took to travel from 8 a.m. to 2 p.m. = 6 h

Mrs Kok's average speed
= 490¹₄ ÷ 6
= 81¹⁷₂₄ km/h

Answer(s): 81¹⁷₂₄ km/h