It's very easy!
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First of all, add up all the amounts of all can flavors.
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What do you think it approximates to?
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I'd say 245.
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Now, how much is 30 out of 245?
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Around 24%.
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So, what's 245/100? (100 because it is default maximum percentage number)
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2.45.
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24 divided by 2.45?
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Around 9%.
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Your best guess is 10% or D.