solve by elimination

Question

2x - y - z =15

4x + 5y + 2z = 10

-x - 4y + 3z = -20

Answer 1

multiply 1st by 3 and add to last equation

6x -3y -3z = 45

-x -4y +3z = 20

5x -7y = 65

multiply 1st by 2 and add to 2nd equation

4x-2y -2z = 30

4x +5y +2z=10

8x + 3y = 40

multiply by 5 to get 40x+15y =200

multiply 5x-7y = 25 by 8 to get 40x -56y = 200

subtract to get-31y =0

y =-0

5z =-25

z= -5

x = 5

2(5) +5 = 15

4(5)+2(-5) = 10

-5 +3(-5) =-20

(x,y,z) = (5,0,-5)