# Solve by Substitution x-3y-z=9 , -x+8y-4z=-24 , 2x-15y+7z=45

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Move all terms not containing to the right side of the equation.
Add to both sides of the equation.
Add to both sides of the equation.
Replace all occurrences of with in each equation.
Replace all occurrences of in with .
Simplify .
Simplify each term.
Apply the distributive property.
Simplify.
Multiply by .
Multiply by .
Subtract from .
Replace all occurrences of in with .
Simplify .
Simplify each term.
Apply the distributive property.
Simplify.
Multiply by .
Multiply by .
Subtract from .
Solve for in the first equation.
Move all terms not containing to the right side of the equation.
Subtract from both sides of the equation.
Subtract from both sides of the equation.
Subtract from .
Divide each term by and simplify.
Divide each term in by .
Cancel the common factor of .
Cancel the common factor.
Divide by .
Simplify each term.
Divide by .
Cancel the common factor of .
Cancel the common factor.
Divide by .
Replace all occurrences of with in each equation.
Replace all occurrences of in with .
Simplify .
Simplify each term.
Apply the distributive property.
Multiply by .
Combine the opposite terms in .
Subtract from .
Subtract from .
Replace all occurrences of in with .
Simplify .
Simplify each term.
Apply the distributive property.
Multiply by .
Subtract from .