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Algebra/substitution

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Expert: - 9/29/2009


Question
solve the system using substitution.

x-6y=64
9y-10x=-181

Answer
From the first equation, we can add 6y to both sides and get x = 64+6y.

This can be substituted into the second equation to get 9y - 10(64+6y) = -181.

This multiplies out to 9y - 640 - 60y = -181.

Add 650 to both sides and combine the y's to get -51y = 459.

This gives y = -9.

Putting in the first equation gives x + 54 = 64, so x is 10.
Checking by using the second equatiion gives -81 - 100, which is -181, as it should be.

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