Each person should ride the bike for 4 miles, so that every one has to walk 8 miles and ride 4 miles.
If they had 2 bikes, each person will ride for 8 miles, 4 miles on each bike, and then walk 4 miles.
(I'm guessing you mean ton)
10 ton = 20,000 pounds
Looks like 49 and w complete the 77 angle
77-49 = w
W= 28