See the lesson plan . The left-right processing of an equation is introduced. See the lesson plan . A response to a request can also make requests. This lesson introduces the nested nature of problem solution steps that arise in this case.
Nested requests are very common in problem solving.
See the lesson plan . The solutions so obtained have an hierarchical structure. Hierarchical organization of information is an effective, widely used, means of communication. See the lesson plan . This lesson provides an overview of the principles involved.