The average (arithmetic mean) of \(3\) positive integers, \(x, y,\) and \(z,\) is \(20.\) If the average (arithmetic mean) of \(x\) and \(y\) is \(9,\) what is the average (arithmetic mean) of \(y\) and \(z?\)

(1) The average (arithmetic mean) of \(x\) and \(z\) is \(22.5.\)
(2) \(y = 5x.\)

Answer: D

Source: GMAT Prep