0\ \Rightarrow \frac{12}{3n-80} >0\ \Rightarrow 3n-80 >0 \Rightarrow n>\frac{80}{3} =26\frac{2}{3} \Rightarrow n=27" alt="a_n=\frac{12}{3n-80} \\ a_n>0\ \Rightarrow \frac{12}{3n-80} >0\ \Rightarrow 3n-80 >0 \Rightarrow n>\frac{80}{3} =26\frac{2}{3} \Rightarrow n=27" align="absmiddle" class="latex-formula">
Ответ: 12