a) 

$12\%=\frac{12}{100}=\frac{12:4}{100:4}=\frac{3}{25}$

$4,5\%=\frac{4,5}{100}=\frac{45}{1000}=\frac{45:5}{1000:5}=\frac{9}{200}$

$148\%=\frac{148}{100}=\frac{148:4}{100:4}=\frac{37}{25}=1\frac{12}{25}$ $148\%=\frac{148}{100}=\frac{148:4}{100:4}=\frac{37}{25}=1\frac{12}{25}$

$0,2\%=\frac{0,2}{100}=\frac{2}{1000}=\frac{1}{500}$

$235\%=\frac{235}{100}=\frac{235:5}{100:5}=\frac{47}{20}=2\frac{7}{20}$

b) 

$0,2=\frac{2}{10}=\frac{20}{100}=20\%$

$0,0046=\frac{46}{10000}=\frac{0,46}{100}=0,46\%$

$\frac{4}{25}=\frac{4\cdot 4}{25\cdot 4}=\frac{16}{100}=16\%$

$\frac{5}{16}=0,3125\cdot 100\%=31,25\%$

$\frac{24}{5}=\frac{24\cdot 20}{5\cdot 20}=\frac{480}{100}=480\%$

$\frac{35}{8}=4,375\cdot 100\%=437,5\%$