Question

please help? i'm stuck.
what is the x coordinate of the solution to the system?
2x-y-z=11
x+y-4z=-1
-x+3y+z=-10

Answer 1

x + y - 4z = -1
-x + 3y + z = -10
----------------add
4y - 3z = -11

2x - y - z = 11
x + y - 4z = -1 -- multiply by -2
-------------
2x - y - z = 11
-2x - 2y + 8z = 2
-------------add
-3y + 7z = 13

4y - 3z = -11 --multiply by 3
-3y + 7z = 13 -- multiply by 4
------------
12y - 9z = -33
-12y + 28z = 52
------------add
19z = 19
z = 1

-3y + 7z = 13
-3y + 7(1) = 13
-3y + 7 = 13
-3y = 13 - 7
-3y = 6
y = -6/3
y = -2

x + y - 4z = -1
x + (-2) - 4(1) = -1
x - 2 - 4 = -1
x - 6 = -1
x = -1 + 6
x = 5

check...
2x - y - z = 11
2(5) - (-2) - 1 = 11
10 + 2 - 1 = 11
12 - 1 = 11
11 = 11 (correct)

x = 5, y = -2 and z = 1