\frac{40}{100}*\frac{52}{10}=\frac{2080}{1000}=2,08%
\frac{10}{100}*30=\frac{300}{100}=3 ; 30+3=33
\frac{10}{100}*\frac{52}{10}=\frac{520}{1000}=0,52 ; 5,2+0,52=5,72
\frac{20}{100}*30=\frac{60}{10}=6 ; 30-6=24
\frac{20}{100}*\frac{52}{10}=\frac{1040}{1000}=1,04 ; 5,2-1,04=4,8