\"\"

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A proportion must use comparable ratios. Because the fraction on the left compares pencils to cost, the fraction on the right must do likewise, so it be  \"\".

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The proportion is \"\".

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\"\"                (Compare denominators)

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\"\"                  (Find the value of x using multiple of denominator)

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\"\"                                   (Multiply: \"\")

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Cost of 30 pencils is $5.00.\"\"

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Cost of 30 pencils is $5.00.