Cramer's Rule was mentioned in the 26th lecture of Zhang Yu's Elective Course of Postgraduate Mathematics. The lecturer was Zhang Yu, a famous expert in postgraduate mathematics counseling and a "key teacher of national excellent curriculum construction" by the Ministry of Education.
Cramer's rule, also translated as Cramer's rule, is a theorem about solving linear equations in linear algebra. It is suitable for linear equations with the same number of variables and equations. It was published by the Swiss mathematician Clem in 1750's Introduction to Linear Algebraic Analysis.