I could not find the page /mooculus/linearAlgebra/systemsOfLinearEqutaions/solvingSystemsOfLinearEquations/notationForLinearEquations but I will look into the cause of this error.
/mooculus/linearAlgebra/systemsOfLinearEqutaions/solvingSystemsOfLinearEquations/notationForLinearEquations
In the meantime, perhaps look at mooculus to find what you seek.
mooculus