This is all about matrices, I don't really get them. Any help is great.

See Explanation
Step-by-step explanation:
1)
[tex] \begin{bmatrix} - 3 & 5 & 6\\-3 & 0 & - 3\end{bmatrix} -\begin{bmatrix} 6 & - 1& 1\\0& - 4& - 5\end{bmatrix} \\\\
=\begin{bmatrix} - 3-6 & 5-(-1) & 6-1\\-3-0 & 0-(-4) & - 3-(-5)\end{bmatrix} \\\\
=\begin{bmatrix} - 3-6 & 5+1 & 6-1\\-3-0 & 0+4 & - 3+5\end{bmatrix} \\\\
=\begin{bmatrix} - 9 & 6 & 5\\-3 & 4 & 2\end{bmatrix} \\\\
[/tex]
2)
[tex] \begin{bmatrix} 4 & - 6 \\-3 & - 6\\2 & 6 \end{bmatrix} + \begin{bmatrix} 5 & 3 \\-5 & 5\\ 4 & - 5\end{bmatrix} \\\\
= \begin{bmatrix} 4 +5& - 6+3 \\-3+(-5) & - 6+5\\2+4 & 6+(-5) \end{bmatrix} \\\\
= \begin{bmatrix} 4 +5& - 6+3 \\-3-5 & - 6+5\\2+4 & 6-5 \end{bmatrix} \\\\
= \begin{bmatrix} 9& - 3 \\-8 & - 1\\6 & 1\end{bmatrix} \\\\[/tex]