Here, $A$ is the coefficient matrix, $X$ is the variable matrix, and $B$ is the constant matrix.
The coefficient matrix $A$ is:
$$
A=\begin{bmatrix}
2 & 6 & 6 \\
2 & 7 & 6 \\
2 & 7 & 7
\end{bmatrix}
$$
The variable matrix $X$ is:
$$
X=\begin{bmatrix}
x \\
y
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