The values of variables X, Y, Z can be easily calculated. View this video for more information.brTo change the Mode of the casio fx-991ms follow the following steps- click the Mode botton for 3 times select the (EQN-1) option select the unknown s and do the .br Today Ill tell you how to .brDemonstration of the use of the Casio fx-991ES PLUS calculator in matrix mode. Using the equation mode for an augmented matrix solving a system of .