It is 10 3/5 miles from alston to barton and 12 1/2 miles from barton to chester. the distance from alston to durbin, via barton and chester is 35 miles. how far is ti from chester to durbin?

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?