Answer
Answers may vary, but there are two 3 x 3 matrices in the attached image (along with the resulting sum).
Work Step by Step
$[1 1 1 ] + [2 3 4]$
$[1 1 1 ] + [5 6 7]$
$[1 1 1] + [8 9 10]$
The three elements of the first row are added to each other.
$1+2=3$
$1+3=4$
$1+4=5$
The three elements of the second row are added to each other.
$1+5=6$
$1+6=7$
$1+7=8$
The three elements of the third row are added to each other.
$1+8=9$
$1+9=10$
$1+10=11$
Resulting matrix:
$[3 4 5]$
$[6 7 8]$
$[9 10 11]$
