The compound interest on Rs. $30000$ at $7\%$  p.a is $4347$ . The time period is

$C.I=A-P$

$4347=A-30000$

$4347+30000=A$

$A=Rs.34347$

$A=P{\left(1+\frac{R}{100}\right)}^n$

$\begin{array}{c}34347=30000{\left(1+\frac{7}{100}\right)}^n\\ \end{array}$

$\frac{34347}{30000}={\left(\frac{107}{100}\right)}^n$

$\frac{11449}{10000}={\left(\frac{107}{100}\right)}^n$

${\left(\frac{107}{100}\right)}^2={\left(\frac{107}{100}\right)}^n$

$n=2$ (Bases are equal power should be equal)