Representing systems of equations with matrices | Matrices | Precalculus | Khan Academy

Given a system of 3 linear equations with 3 variables, we can represent it with the equation Ax=b, where A is a 3x3 matrix, x is a 3D vector with the variables, and b is a constant 3D vector. Why is this useful? We can solve the system by solving the equation, which in many cases is much more efficient.