Solve by substitution elimination or matrix methods x y 4

Solve by substitution, elimination, or matrix methods. x + y = -4

x - z = 1

x + 2y + 3z = -21

Solution

substitution

x + y = -4 =>y=-4-x

x - z = 1=>z=x-1

x + 2y + 3z = -21

substitute y ,z

x + 2(-4-x) + 3(x-1) = -21

x-8-2x+3x-3=-21

2x=21+11

x=16

substitute x=16 in y=-4-x

=>y=-4-16

=>y=-20

substitute x=16 in z=x-1

z=16-1

z=15

solution is (x,y,z)=(16,-20,15)