Theo đề bài ta có:
\(\frac{2n+1+1}{12n+2n+1+17}.100\%=13,51\left(\%\right)\)
\(\Leftrightarrow\frac{2\left(n+1\right)}{2\left(7n+9\right)}=\frac{13,51}{100}\\ \Leftrightarrow\frac{n+1}{7n+9}=\frac{13,51}{100}\\ \Leftrightarrow100n+100=94,57n+121,59\\ \Leftrightarrow5,43n=21,59\\ \Leftrightarrow n=\frac{21,59}{5,43}\approx4\)
%H = (2n+2)/(14n+18) *100% = 13.51%
=> n = 4