Prerequisite section mention of high school math links to FAQ

Author: waciumawanjohi

README.md

@@ -108,7 +108,7 @@ just remember that you can't purchase success!
 
 ## Prerequisites
 
-- [Core CS](#core-cs) assumes the student has already taken [high school math](https://www.khanacademy.org/math/high-school-math), including algebra, geometry, and pre-calculus.
+- [Core CS](#core-cs) assumes the student has already taken [high school math](https://github.com/ossu/computer-science/blob/master/FAQ.md#how-can-i-review-the-math-prerequisites), including algebra, geometry, and pre-calculus.
 - [Advanced CS](#advanced-cs) assumes the student has already taken the entirety of Core CS
 and is knowledgeable enough now to decide which electives to take.
 - Note that [Advanced systems](#advanced-systems) assumes the student has taken a basic physics course (e.g. AP Physics in high school).