Add up the matrices $$\left( \begin{array}{ccc} 3 & 6 & 7 \\ 0 & 2 & 3 \\ 0 & -4 & 2 \end{array} \right) + \left( \begin{array}{ccc} 2 & 5 & 4 \\ 2 & 0 & -6 \\ 2 & 7 & 1 \end{array} \right)$$
See development and solution
Development:
$$\left( \begin{array}{ccc} 3 & 6 & 7 \\ 0 & 2 & 3 \\ 0 & -4 & 2 \end{array} \right) + \left( \begin{array}{ccc} 2 & 5 & 4 \\ 2 & 0 & -6 \\ 2 & 7 & 1 \end{array} \right) = \left( \begin{array}{ccc} 3+2 & 6+5 & 7+4 \\ 0+2 & 2+0 & 3-6 \\ 0+2 & -4+7 & 2+1 \end{array} \right) = \left( \begin{array}{ccc} 5 & 11 & 11 \\ 2 & 2 & -3 \\ 2 & 3 & 3 \end{array} \right)$$
Solution:
$$\left( \begin{array}{ccc} 5 & 11 & 11 \\ 2 & 2 & -3 \\ 2 & 3 & 3 \end{array} \right)$$