ShmoopTube

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And here's your shmoop de jour...

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Solve for y using substitution: 2x + 4y = 16

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x + 3y = 12

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And here are the potential answers...

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OK, so what is this question asking?

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Questions like this one are algebra's version of... puzzles. Except you don't have to

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worry about getting that cardboard dust all over yourself.

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The key is to isolate one of the variables cleanly...

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...i.e. figure out just what y equals and then shove that result into the other equation

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so we can get a real answer.

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It doesn't matter which equation we solve, but let's start with the second because...

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it's there. And we already have a variable all by its lonesome.

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We can rewrite it as x equals 12 minus 3y.

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So now, everywhere we see an "x" we can just substitute "12 minus 3y."

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If we do so in the first equation, we get 2 times the quantity 12 minus 3y... plus the

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4y and equals 16.

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Distribute the 2 and we have 24 minus 6y plus 4y equals 16.

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Simplify to get 8 minus 2y equals zero...

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...and then 8 = 2y.

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Then if we divide both sides by 2 and we get y equals... 4.

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Answer C.

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As in, "Cardboard dust."

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