Doug has saved some money for a new guitar that costs $127, but needs to save more. He writes an addition equation with a variable to represent the amount of money that he still needs to save.

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?