How do you solve -x-y-3z=-9 z=3x-1 x-5y+z=21 using elimination

Assuming these are three separate problems, I have solved them for you below.

1.)

Multiply the whole thing by -1 so x is positive.

2.)

⇒

⇒

Isolate x⇒

⇒

3.)

⇒

⇒

⇒

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