Solve the system by substitution.

-x-y-z=-8
-4x+4y+5z=7
2x+2z=4

I am very confused about this. Can someone please explain how to do this?

4 answers

The actual steps will vary from person to person, and there is no single way to solve this.
You sort of have to decide on the simplest equation as a starting point.
In this case it is the last equation, it only has two variables.
2x + 2z = 4 , or
x + z = 2 ---> x = 2-z
I will now sub that into the 1st and the 2nd

-x-y-z=-8 ----> x + y + z = 8
2-z + y + z = 8
y = 6 ----> well that was lucky

in the 2nd:
-4x + 4y + 5z = 7
-4(2-z) + 24 + 5z = 7
-8 + 4z + 24 + 5z = 7
9z = -9
z = -1
then x = 2-z = 2+1 = 3

x = 3
y = 6
z = -1

THANK YOU!!!!!!!!!!

you are welcome

8 x 4 = 32 not 24 XD