8m-12-6m+4m help I suck at math​

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?

Which expression and diagram represent “renee biked four times as far this month as last month”?

Which polygon is she in the process of constructing ?