Question

What Is The Solution To The System?
3x+y+z=7
x+3y-z=13
y=2x-1
A.)(7,13,-1)
B.)(3,2,-2)
C.)(2,3,-2)
D.)(-2,3,2)

Answer 1

plug equation 3 into 1 and 2 :

3x + (2x-1) + z = 7
x + 3(2x-1) -z = 13

5x + z = 8
7x - z = 16

add the equations :

12x = 24
x=2

plug x=2 into y=2x-1 to get:

y = 3

plug x=2 into either 5x + z = 8 or 7x - z = 16 to get:

14 -z = 16
z = -2

(2,3,-2)

Answer 2

Thanks