Question 72962
Distance(d) = rate(r) times time(t) or d=rt and r=d/t

Let r= Joe's rate (how fast he's walking) 

In 2 hours Jill walks 2 kilometers (d=1*2) that leaves 6 kilometers (8-2) for Joe to walk in 2 hours

r=6/2=3 kilometers/hour-----------------------------------Joe's speed

CK

1 kilometer/hour times 2 hours plus 3 kilometers/hour times 2 hours =8 kilometers
8 kilometers=8 kilometers
Both together walked 8 kilometers

Hope this helps-----ptaylor