Tourists were on a hiking trip for three days. On the first day, they hiked 1/8 of the trail. On the second day they hiked 4/7 of the remaining trail. On the third day they hiked 1/3 of the remaining trail and the last 8 km. How many km is the whole trail? 

Let x be the trail length

The first day they hiked (1/8)x

The second day they hiked :

(4/7) [ x - 1/8x]  =   (4/7) (7/8)x = (1/2)x

The third day they hiked :

(1/3) [ x - (1/8)x - (1/2)x] + 8  =  (1/3) (3/8)x + 8 =   (1/8)x + 8

So

(1/8)x + (1/2)x + (1/8)x + 8  = x     simplify

(3/4)x + 8 = x      subtract (3/4)x fro both sides

8  = (1/4)x      multiply both sides by 4

32  = x  =  32km  is the trail length

Let the the trail=T km

.875 X 3/7 X 2/3T=8

.25T=8 divide both sides by .25

T=8/.25=32 Km-the length of the trail.