$a=3^2\cdot {10}^5$  

 

$b={10}^3\cdot {30}^2=$  

  

$={10}^3\cdot {\left(10\cdot 3\right)}^2=$  

$={10}^3\cdot {10}^2\cdot 3^2=$  

$={10}^{3+2}\cdot 3^2=$  

$={10}^5\cdot 3^2=a$