[tex]\displaystyle\\
\text{20\% din 75} = 20\% \times 75 = \frac{20}{100}\times 75=\\\\
=\frac{20\times75}{100}=\frac{75}{5}=\boxed{\bf 15}\\\\\\
\text{75\% din 312}= 75\% \times 312 = \frac{75}{100}\times 312=\\\\
=\frac{75\times312}{100}=\frac{3\times 312}{4}=3\times 78=\boxed{\bf 234}[/tex]
