Passage: Born in New York City, Karp grew up on the Upper West Side of Manhattan. His parents are Barbara Ackerman, a science teacher from San Anselmo, California, and Michael D. Karp, a film and television composer. He has a younger brother named Kevin.  His parents separated when he was 17. Karp attended the Calhoun School from pre-school through eighth grade, where his mother teaches science. At 11, he began learning HTML and began designing websites for businesses. Karp went on to attend The Bronx High School of Science for one year before dropping out when he was 15 and started homeschooling. At the time, Karp had aspirations of attending college in New York, or going to MIT and saw homeschooling and doing other projects on the side as a way to impress the colleges. Karp never returned to high school or earned his high school diploma.

Question: Karp was what age when he learned HTML?
11