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@@ -26,10 +26,10 @@ Courses | School | Duration | Effort | Frequency | Prerequisites
 
 Courses | School | Duration | Effort | Frequency | Prerequisites
 :-- | :--: | :--: | :--: | :--: | :--:
-[Calculus 1A: Differentiation](https://mitxonline.mit.edu/courses/course-v1:MITxT+18.01.1x/) | MIT | 12 weeks | 6-10 hours/week | self-paced | [pre-calculus](https://www.edx.org/course/precalculus-asux-mat170x)
+[Calculus 1A: Differentiation](https://mitxonline.mit.edu/courses/course-v1:MITxT+18.01.1x/) | MIT | 12 weeks | 6-10 hours/week | self-paced | [pre-calculus](https://www.edx.org/learn/precalculus/arizona-state-university-precalculus)
 [Calculus 1B: Integration](https://mitxonline.mit.edu/courses/course-v1:MITxT+18.01.2x/) | MIT | 15 weeks | 6-10 hours/week | self-paced | Calculus 1A: Differentiation
 [Calculus 1C: Coordinate Systems & Infinite Series](https://mitxonline.mit.edu/courses/course-v1:MITxT+18.01.3x/)| MIT | 8 weeks | 6-10 hours/week | self-paced | Calculus 1B: Integration
-[Linear Algebra - Foundations to Frontiers](https://www.edx.org/course/linear-algebra-foundations-to-frontiers) | UT Austin | 15 weeks | 6-10 hours/week | self-paced | [pre-calculus](https://www.edx.org/course/precalculus-asux-mat170x)
+[Linear Algebra - Foundations to Frontiers](https://www.edx.org/course/linear-algebra-foundations-to-frontiers) | UT Austin | 15 weeks | 6-10 hours/week | self-paced | [pre-calculus](https://www.edx.org/learn/precalculus/arizona-state-university-precalculus)
 [Introduction to Probability and Data](https://imp.i384100.net/9WZ4E0) | Duke | 5 weeks | 5-7 hours/week | twice a month | none
 [Intro to Statistics ](https://click.linksynergy.com/deeplink?id=PtFMiHYfEVk&mid=53187&murl=https%3A%2F%2Fwww.udacity.com%2Fcourse%2Fintro-to-statistics--st101) | Udacity | 8 weeks | 5-7 hours/week | self-paced | none