A=f(18)=110(.8855)^18=12.3mg
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Explanation:
Plug in t = 18 to get
f(t) = 110*(0.8855)^t
f(18) = 110*(0.8855)^18
f(18) = 110*(0.112045)
f(18) = 12.32495
f(18) = 12.32
The answer is approximate. I rounded to two decimal places (aka to the nearest hundredth).
