Ardi and Lei are both travelling by train. Ardi's train travels 70 km in 35 minutes.
Lei's train travels 585 km.
It leaves at 9:05 and arrives at 13:35.
Work out the difference, in km/h, between the average speed of their trains.

10 kilometer/hour

Step-by-step explanation:

Average speed = Total distance travelled / Total time taken

Ardi:

Total distance travelled = 70 km

Total time taken = 35 minutes = 35/60 hour

Average speed = Total distance travelled / Total time taken

= 70 km ÷ 35/60 hr

= 70 × 60/35

= 4,200/35

= 120 kilometer/hour

Lei:

Total distance travelled = 585 km Total time taken = 9:05 - 13:35 = 4 hours 30 minutes

= 4.5 hours

Average speed = Total distance travelled / Total time taken

= 585 km / 4.5 hours

= 130 kilometer/hour

Difference, in km/h, between the average speed of their trains = Lei's train - Ardi's train

= 130 kilometer/hour - 120 kilometer/hour

= 10 kilometer/hour

x = -4

step-by-step explanation:

- 20 - 4(x + 3) = 4x

=> -20 - 4x - 12 = 4x

=> - 32 -4x = 4x

=> -32 = 4x + 4x

=> - 32 = 8x

=> -32/8 = x

=> -4 = x