3. Which sequence has a common difference of three? * O 3, 12, 21, 30,..
2,6, 18, 54, ...
o 21, 18, 15, 12,...
O 7, 10, 13, 16,

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?