If Cyrus knows that △ABC∼△EDC and AB∥ED, how can he prove that line m passing through AB has the same slope as line l passing through ED?

B.

Step-by-step explanation:

According to what it's drawn in the diagram Cyrus can prove the above by considering the fact that the both triangles are similar triangles.

The second thing he will consider is that the the slope will be equal be equating the formula for the both slopes of the triangle.

He should also Consider multiplication property, in that way, when all these three factors are present in his equation he should be able to show his proof.

3 is greater then both of those numbers