The default matrix WebAssign gives you when entering a matrix may not be the right size that you need to answer that question. Many problems are set with a default size of 2x2, and you will need to adjust the matrix size depending on the final answer. 

You can use the "down" arrow to add rows and the "up" arrow to delete rows. You can use the "right" arrow to add columns and the "left" arrow to delete columns.

Here is a video that walks you through the process of graphing in WebAssign.

There are two ways to type variables with subscripts.

1. Use the underscore button on your keyboard (press shift and then the button to the right of the 0). The cursor will move down, and you can type in the appropriate subscript. Then, click the right arrow on your keyboard to move back to the regular line.

2. Use the calc pad. Click on "Functions," then click the top left button (the one with two boxes on it). That will move the cursor down, and you can type in the appropriate subscript. Then, click the right arrow on your keyboard to move back to the regular line.