If $\frac{3+5+7+....n terms}{5+8+11+....10 terms}$, then the value of n is

$\frac{3+5+7+....n terms}{5+8+11+....10 terms}$=7

$\begin{array}{l}\Rightarrow \frac{\frac{n}{2}[6+(n-1)2]}{\frac{10}{2}[10+9.3]}=7\\ \Rightarrow \frac{\frac{n}{2}[2n+4]}{5.37}=7\\ \Rightarrow n(n+2)=35.37\\ \Rightarrow n=35\end{array}$