(3 2 4 0) (x y)=(7 12) find x and y in this matrices

Answer 1

3x+2y=7
4x+0y=12

x=3
y=-1

or, with a lot more work,

(x y) = (3 2 4 0)^-1 * (7 12)
= 1/8 (0 2 4 3)(7 12) = 1/8 (24 -8) = (3 -1)