The following is an alteration of an assignment given in a TVMHS math class. The teacher normally has the students use the markup tools in Khan Academy to solve problems like this.
In this case, the teacher could post their own problem, or a problem from a PDF version of an exam, leave video and voice instructions from within Kami, assign a copy of the problem for students, and they can show their work with Kami annotation tools, and explain their thinking using Voice or Video comments. Students click "Turn in" and their work is shared back to the teacher, who can then mark up their work using Kami annotation tools (drawing, voice/video/text comments, highlighters, etc.) See screencast examples below!
Student Process for Authorizing Kami Extension
Kami Overview for Teachers