I NEED HELP!

I have a lesson due by Friday and I am not understanding just exactly what I am being required to do. Here is the situation:

Given:

 The practical applications of ratio, proportion, and percent in real-world situations are so numerous that students need to acquire the ability to perceive and determine relationships between these concepts.

 Task:

A. Using the attached lesson plan format, design an original lesson plan to teach proportional reasoning when solving percent problems in grades 5–8.
 
B. In your lesson plan, include activities that allow for the following experiences:

1. Students discover, develop, derive, and conceptually understand the cross-product algorithm via conceptually based approaches such as the line segment model.

I'm not sure that I conceptually understand the cross-product algorithm.

Can anyone shed light on me or direct me to a resource that may help me?

Thanks!