Question

Which is the solution to the following system x+2y+z=9
X-y+3z=13
2z=10

Answer 1

2z = 10
/2 on both sides
z = 5
———————
x + 2y + z = 9
x + 2y + 5 = 9
-5 on both sides
x + 2y = 4
———————
x - y + 3z = 13
x - y + 3(5) = 13
x - y + 15 = 13
-15 on both sides
x - y = -2
———————
x + 2y = 4
x - y = -2

x + 2y = 4
- (x - y = -2)

x + 2y = 4
-x + y = 2
Add the equation together
3y = 6
/3 on both sides
y = 3
———————
Substitute z = 5 and y = 3 in one of the equations that includes all of the variables
x + 2y + z = 9
x + 2(3) + 5 = 9
x + 6 + 5 = 9
x + 11 = 9
-11 on both sides
x = -2
———————

Answers:
x = -2
y = 3
z = 5

Answer 2

Explanation:

I'm not sure but,here you go

2z = 10

z = 10 ÷ 2 = 5

x + 2y + z = 9

x + y + 3z = 13

____________

x + 2y + 5 = 9

x + y + 3(5) = 13

_____________

x + 2y = 9 - 5

x + y = 13 - 15

___________

x + 2y = 4

x + y = -2 (×-1)

___________

x + 2y = 4

-x - y = 2

___________

y = 6

x = -2y - z + 9 = -2(6) - 5 + 9 = -12 - 5 + 9 = -8

If you wanna check,

x + y +3z = 13

(-8) + 6 + 3(5) = 13

x = -8 , y = 6 , z = 5

I'm not very sure but here you go,I might be wrong^^