Casio fx-991EX Quick Start Manual page 16

MATRIX
Enter the values of the coefficients, pressing p after each
one to move to the next value.
Press C to return to the Matrix Calculation screen.
The solution can be found by calculating A x B.
-1
Press i3(MatA)uOi4(MatB)p.
The solution represents the following:
This same system can also be solved using the Equation icon.
16 fx-991EX Quick Start Guide