Question

Solve the system by substitution.
2x-y+z=-4
z=5
-2x+3y-z+-10
Possible answers:
1. -8,7,5
2. -8,-7,5
3. 8,-7,5
4. -8,-7,-5
I'm so confused I don't even know where to start please help!

Answer 1

z=5
z is already given, so just solve the equation as if it were this
2x- y + 5 = -4
-2x +3y - 5 = -10

add the equations
2y = -14
y = -7

2x +7 + 5 = -4
2x + 12 = -4
2x = -16
x = -8

Answer 2

Do you understand? or should I explain it a bit more?...

Answer 3

Yeah I'm really bad at math I'm still a bit confused @shamil98

Answer 4

Okay.
so you have 3 equations
2x-y+z=-4
-2x+3y-z = -10
z=5
you see the z variables in the other two equations? you just input the 5 since z = 5.

This then becomes
2x - y + 5 = -4
-2x +3y -(5)= -10
So far so good?...

Answer 5

Okay I understand that part

Answer 6

2x -2x = 0 so that means you can solve for y
so just add these equations

2x - y + 5 = -4
-2x +3y -(5)= -10
-----------------
0 +2y + 0 = -14
2y = -14

2y/2 = -14/2

y = -7

Answer 7

You know have two variables done, just x to go.
so you input those values in one of the original equation.
2x-y+z=-4
2x -(-7) +(5) = -4

Answer 8

then add them or?

Answer 9

2x + 7 + 5 = -4
2x + 12 = -4
-12 -12

2x = - 16
2x/2 = -16/2
x = -8

Answer 10

Yes, you add that and solve for x.

Answer 11

So the second choice -8,-7,5?

Answer 12

Yep.

Answer 13

Thank you so much I actually understood most of what you said(: