Question: how long does it take to complete khan academy math?
Answer: So maybe an average of 300 minutes per skill, across all 390 skills -- that's 1950 hours, or 11+ years of work (at 180 hr/yr). You'd probably finish more slowly than your fellow students that went to high school and took 8 semesters of math in college. It depends *SO* heavily upon your level of determination.