Answer
$\left[\begin{array}{rrr}
4 & -1 & -1\\
5 & 1 & 2
\end{array}\right]$
Work Step by Step
$A=\left[\begin{array}{lll}
1 & -1 & 0\\
0 & 2 & 1
\end{array}\right],\quad B=\left[\begin{array}{lll}
3 & 0 & -1\\
5 & -1 & 1
\end{array}\right],\quad C=\left[\begin{array}{lll}
x & 1 & w\\
z & r & 4
\end{array}\right]$
$(A+B)_{ij}=A_{ij}+B_{ij}$
ijth entry of the sum = sum of the ijth entries
------------
$A+B=\left[\begin{array}{lll}
1+3 & -1+0 & 0+(-1)\\
0+5 & 2+(-1) & 1+1
\end{array}\right]=\left[\begin{array}{lll}
4 & -1 & -1\\
5 & 1 & 2
\end{array}\right]$
