Question 215965
x-3y=6
3x+y=-22 
.
coefficient matrix:
1 -3
3 1 
Det of coefficients: (1-(-9)) = 10
.
x-matrix
6   -3
-22 1
Detx: 6 - 66 = -60
.
y-matrix
1 6
3 -22
Dety: -22 - 18 = -40
.
x = Detx/Detcoef = -60/10 = -6
y = Dety/Detcoef = -40/10 =  -4
.