I got it its this answer i used mathpapa for this
Without needing fancy formulas, we can conclude that after 10 years, half of the substance will be left. So, we can make our own formula:
amount remaining = 1 / 2^(years/10)
So, after 5 years
amount remaining = 1 / 2^(5/10)
amount remaining = 1 / 2^(.5)
amount remaining = 1 /
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<span>
<span>
1.414213562
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</span></span><span>amount remaining = 0.70711 * 20 grams
</span><span><span><span><span>amount remaining = </span>14.1421356237 grams
</span></span></span>
You start by distributing: 8s-4=7s+12
Combine like terms: 8s-7s=12+4
Solve and get your answer: s=16
