$\text{a)}60\%\cdot x=300$   

$\frac{{\sout{60}}^3}{{\sout{100}}^5}\cdot x=300\mid \cdot \frac{5}{3}$  

$x={\sout{300}}^{100}\cdot \frac{5}{{\sout{3}}^1}$  

$x=500$  

 

$\text{b)}15\%\cdot x=42$  

$\frac{{\sout{15}}^3}{{\sout{100}}^{20}}\cdot x=42\mid \cdot \frac{20}{3}$ $\frac{{\sout{15}}^3}{{\sout{100}}^{20}}\cdot x=42\mid \cdot \frac{20}{3}$   

$x={\sout{42}}^{14}\cdot \frac{20}{{\sout{3}}^1}$  

$x=280$  

 

$\text{c)}20\%\cdot x=4,6$    

$\frac{{\sout{20}}^1}{{\sout{100}}^5}\cdot x=4,6\mid \cdot 5$      

$x=23$    

 

 

$\text{d)}4\%\cdot x=0,2$  

$\frac{{\sout{4}}^1}{{\sout{100}}^{25}}\cdot x=0,2\mid \cdot 25$      

$x=5$  

 

$\text{e)}7\%\cdot x=14$   

$\frac{7}{100}\cdot x=14\mid \cdot \frac{100}{7}$      

$x={\sout{14}}^2\cdot \frac{100}{{\sout{7}}^1}$  

$x=200$  

 

$\text{f)}125\%\cdot x=55$  

$\frac{{\sout{125}}^5}{{\sout{100}}^4}\cdot x=55\mid \cdot \frac{4}{5}$     

$x={\sout{55}}^{11}\cdot \frac{4}{{\sout{5}}^1}$  

$x=44$  

 

$\text{g)}1,8\%\cdot x=9$   

$0,018\cdot x=9$      

$x=9:0,018$   

$x=500$      

 

$\text{h)}0,2\%\cdot x=5,1$  

$0,002\cdot x=5,1$      

$x=5,1:0,002$   

$x=2550$