Mrs Lu left home at 7 a.m. and drove towards the city. 2¹₄ hour later, Mr Lu left the house and drove at an average speed of 104 km/h towards the city. When Mr Lu reached his destination at 1 p.m., Mrs Lu was 10 km away from the city. Find Mrs Lu’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₄ h = ¹₄ x 60 = 15 min
2¹₄ = 2 h 15 min

2 h 15 min after 7 a.m. = 9.15 a.m.

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

Time that Mr Lu took from 9.15 a.m. to 1 p.m. to reach his destination = 3 h 45 min

1 min = ¹₆₀ h
45 min = ⁴⁵₆₀ h = ³₄ h
3 h 45 min = 3³₄ h

Distance that Mr Lu drove
= 3³₄ x 104
= 390 km

Distance that Mrs Lu drove when Mr Lu reached
= 390 - 10 
= 380 km

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

Mrs Lu's average speed
= 380 ÷ 6
= 63¹₃ km/h

Answer(s): 63¹₃ km/h