Lets take a 3 by 3 matrix. Release the Ctrl and Shift keys. Select Equations in the gallery list.
Begin every formula with an equal sign.
Next highlight the values in the range A2B11. Instead of typing the constants into your formula you can select the cells that contain the values that you want to use and enter the operators in between selecting cells. After you insert the equation the Equation Tools Design tab opens with symbols and structures that can be added to your equation. A basic operation on a matrix in Excel.