$X + Y = \begin{bmatrix}5 & 2 \\ 0 & 9\end{bmatrix}$ and $X - Y = \begin{bmatrix}3 & 6 \\ 0 & -1\end{bmatrix}$. What is $X$?

Explanation

1. 01

   Add the two equations: $2X = \begin{bmatrix}8 & 8 \\ 0 & 8\end{bmatrix}$.

2. 02

   Halve every element: $X = \begin{bmatrix}4 & 4 \\ 0 & 4\end{bmatrix}$.