Latoya drove to the mountains last weekend. there was heavy traffic on the way there, and the trip took 12 hours when latoya drove home, there was no traffic and the trip only took 8 hours

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?