Question 880159
2x-3y=20
12x+8y=-192
I think you copied #1 incorrectly
20 and -192 form 
 the  B matrix (the answers)

the x's are 2 and 12
the y's are -3 and 8
the original matrix was 
2 -3 20
12 8 -192

The first determinant would be 2*8-(-3*12)= 16-(-36)=52
D=52
Dx=160-(-3*-192)=160-576=-416
Dy=-384-240=-624
x=Dx/D-416/52=-8
y=Dy/D=-624/52=-12