Passage: Depp was born in Owensboro, Kentucky, the youngest of four children of Betty Sue Palmer (née Wells), a waitress, and John Christopher Depp, a civil engineer.  Depp moved frequently during his childhood. He and his siblings lived in more than 20 different places, eventually settling in Miramar, Florida in 1970. Depp's parents divorced in 1978 when he was 15. His mother married Robert Palmer, whom Depp has called "an inspiration".With the gift of a guitar from his mother when he was 12, Depp began playing in various garage bands. A year after his parents' divorce, he dropped out of Miramar High School to become a rock musician. He attempted to go back to school two weeks later, but the principal told him to follow his dream of being a musician. He played with The Kids, a band that enjoyed modest local success. The Kids set out together for Los Angeles in pursuit of a record deal, changing their name to Six Gun Method, but the group split up before signing a record deal. Depp subsequently collaborated with the band Rock City Angels and co-wrote their song "Mary", which appeared on Rock City Angels' debut Geffen Records album Young Man's Blues. On December 20, 1983, Depp married Lori Anne Allison, the sister of his band's bass player and singer. During their marriage she worked as a makeup artist while he worked a variety of odd jobs, including a telemarketer for pens. His wife introduced him to actor Nicolas Cage, who advised him to pursue an acting career. Depp and Allison divorced in 1985.

Question: How old was Depp when his parents went their separate ways?
15