How do I get the answer for 20×5000

Consider the proof. given: segment ab is parallel to line de. prove: what is the missing statement in step 5?

How do you use the elimination method for this question? explain, because i really want to understand!

The cross-sectional areas of a right triangular prism and a right cylinder are congruent. the right triangular prism has a height of 6 units, and the right cylinder has a height of 6 units. which conclusion can be made from the given information? the volume of the triangular prism is half the volume of the cylinder. the volume of the triangular prism is twice the volume of the cylinder. the volume of the triangular prism is equal to the volume of the cylinder. the volume of the triangular prism is not equal to the volume of the cylinder.