UNKNOWN DISTANCE
Problem
The sum
of the distances from A to B and C to D is 30 miles. The distance from B to C is 2/3 of the distance from C to
D. The distance from A to B is 3/8
of the distance from B to C. What
is the distance from A to B?
Solution
AB + CD = 30
, 
Now,
substituting AB and CD, we have:
Now that
we have the length of BC, we can find the length of AB.
Reference: Project INTERMATH