Question 585818
<pre>
Remember the word "arc" for a<sub>r,c</sub> or a<sub>rc</sub>.

The "r" stands for the row, the "c" stands for the column.

The columns are vertical (from top to bottom) like the columns on a house 
or building.  The rows go horizontal (from left to right) 

So a<sub>1,2</sub> or a<sub>12</sub> means the element in row 1 (the top row)
and column 2 (the middle column), which is the 2.

Edwin</pre>