9. You are mailing a 21-pound item by parcel post. The total weight of an item and its packaging cannot be greater than 50 pounds. Write and solve an inequality that represents the heaviest the packaging can be without exceeding the 50-pound weight limit.​

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ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

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