Detailed Instructions: In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.
Q: Passage: Audioslave's history dates back to October 18, 2000, when Rage Against the Machine's lead vocalist Zack de la Rocha announced he was leaving the band, citing a breakdown in its "decision-making process". This led to the breakup of Rage Against the Machine, but the remaining three members of the band—Tim Commerford, Tom Morello, and Brad Wilk—decided to stay together and announced plans to continue with a new vocalist. Several vocalists jammed with the three, including B-Real of Cypress Hill, but they did not want another rapper or anybody who sounded like de la Rocha. Contrary to popular belief, Layne Staley of Alice in Chains neither auditioned nor was asked to join the new project. Tom Morello denied this claim on his Twitter account in 2015. Music producer and friend Rick Rubin suggested that they play with Chris Cornell of Soundgarden. Rubin also persuaded the three of them to go into group therapy with performance coach Phil Towle after the breakup. Rubin was confident that with the right new voice, Rage Against the Machine had the potential to become a better band; he believed "it could turn into a Yardbirds-into-Led Zeppelin scenario." Commerford later credited Rubin for being the catalyst that brought Audioslave together. He called him "the angel at the crossroads" because "if it wasn't for him, I wouldn't be here today."
 Link Information: Zacharias Manuel de la Rocha (born January 12, 1970)  Question: How old was Zack when he left Rage Against the Machine?
A:
Answer: 30