Question 263955
the percentage of adult smokers in the U.S. is declining each year. 
If t represents the number of years since 1997, then 
P(t) = -0.51t + 24.675 
represents the corresponding percentage of adults who smoked cigarettes during that year. 
Write an inequality that can be used to determine the first year in which the percentage of adult smokers falls below 15%. 
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15 > -0.51t + 24.675
-0.51t < -9.675
t > 18.97
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Earliest year: 1997+18.97 = 2015.97; rounded up is 2016

Solve the inequality in part a using an algebraic as well as a graphical approach. 
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P(t) = -0.51t + 24.675 
{{{graph(400,300,-40,60,-5,50,15,y<-0.51x+24.675)}}}
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Cheers,
Stan H.