20 von 25 in %
$${\frac{{\mathtt{20}}}{{\mathtt{25}}}} = {\frac{{\mathtt{4}}}{{\mathtt{5}}}} = {\mathtt{0.8}}$$ $${\mathtt{80}}\% = {\frac{{\mathtt{80}}}{{\mathtt{100}}}} = {\frac{{\mathtt{20}}}{{\mathtt{25}}}}$$
$${\frac{\left({\mathtt{20}}{\mathtt{\,\times\,}}{\mathtt{4}}\right)}{\left({\mathtt{25}}{\mathtt{\,\times\,}}{\mathtt{4}}\right)}} = {\frac{{\mathtt{80}}}{{\mathtt{100}}}} = {\mathtt{80}}\%$$