Theo has had three tests in his math class so far. He does the following calculations using the average (mean) of some of his marks.
First he calculates the average of his first and second test marks. Then he calculates the average of this value with his third test mark to get \(74\%\).
First he calculates the average of his second and third test marks. Then he calculates the average of this value with his first test mark to get \(73.5\%\).
First he calculates the average of his first and third test marks. Then he calculates the average of this value with his second test mark to get \(76\%\).
Determine the average his three test marks.