$${\mathtt{6}}{\mathtt{\,-\,}}{\mathtt{12}} = -{\mathtt{6}}$$
http://web2.0rechner.de/fragen/wie-berechnet-man-einen-kredit
http://www.zinsen-berechnen.de/finanzrechner/
$${\frac{{\mathtt{54}}}{{\mathtt{24}}}} = {\frac{{\mathtt{27}}}{{\mathtt{12}}}} = {\frac{{\mathtt{9}}}{{\mathtt{4}}}}$$
$${\frac{{\mathtt{54}}}{{\mathtt{24}}}} = {\frac{{\mathtt{9}}}{{\mathtt{4}}}} = {\mathtt{2.25}}$$ = $${\frac{{\mathtt{225}}}{{\mathtt{100}}}}$$
$${\mathtt{\,-\,}}\left({\mathtt{5.684\: \!341\: \!9}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{-{\mathtt{14}}}\right) = -{\mathtt{0.000\: \!000\: \!000\: \!000\: \!056\: \!8}}$$