Answer:
21
Step-by-step explanation:
[tex]\left[\begin{array}{cc}5&9\\-6&9\end{array}\right] +6\left[\begin{array}{cc}-5&2\\7&8\end{array}\right][/tex]
Multiply the second matrix by 6.
[tex]\left[\begin{array}{cc}5&9\\-6&9\end{array}\right] +\left[\begin{array}{cc}-30&12\\42&48\end{array}\right][/tex]
Add the corresponding cells in each matrix.
[tex]\left[\begin{array}{cc}5-30&9+12\\-6+42&9+48\end{array}\right][/tex]
[tex]\left[\begin{array}{cc}-25&21\\36&57\end{array}\right][/tex]
