welll...you have there written just one relationship...it is berween 280 and 4 hours...you have to figure out speed:
[tex]280 \div 4 = 70[/tex]
it is speed per hour
then you just connect time and speed:
- 140 - 2
- 280 - 4
- 350 - 5
- 420 - 6
- 560 - 8
- 700 - 10
