Thanks, people. Yep, the diagram was on the answer sheet.

I wound up submitting scans of three worksheets, including that one, to the TAT team, at the risk of angering his teacher, to show why the current system isn't working. Anyone can make mistakes, but I really think he deserves to be taught math by a person (and preferably one who has somewhat of a feel for math), instead of being parked in front of a computer or just left to do worksheets. No matter who was administering these worksheets, the communication is just too restricted to constitute teaching, nor is he being taught to a curriculum or at the right level.
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Striving to increase my rate of flow, and fight forum gloopiness. sick