1.5.1 Systems of algebraic equations

Problem: Solve the matrix equation \[ A X=B, A=\left(\begin{array}{cc} 2 & 1 \\ 2 & -1 \end{array}\right), B=\left(\begin{array}{lll} 2 & 1 & 2 \\ 2 & 2 & 1 \end{array}\right) . \]