When you first began writing for an academic English setting, you followed a very straightforward structure. This writing style may seem very direct, but it is expected for basic essays. That structure becomes more flexible with longer essays and more complex topics. The structure may also shrink to one or two paragraphs depending on the expectations for the task.
Regardless of how much writing you are expected to produce for the assignment, all writing will include the same basic structures. So while this textbook may imply a standard 5-paragraph essay length, the same principles will apply when you write a short answer.