Am einfachsten geht es mit dem Rechner:
1.) $${\mathtt{8.25}}{\mathtt{\,-\,}}{\mathtt{25}}\% = {\frac{{\mathtt{99}}}{{\mathtt{16}}}} = {\mathtt{6.187\: \!5}}$$
2.) 25 % von 8.25 = $${\frac{{\mathtt{8.25}}{\mathtt{\,\times\,}}{\mathtt{25}}}{{\mathtt{100}}}} = {\frac{{\mathtt{33}}}{{\mathtt{16}}}} = {\mathtt{2.062\: \!5}}$$ ; $${\mathtt{8.25}}{\mathtt{\,-\,}}{\mathtt{2.062\: \!5}} = {\frac{{\mathtt{99}}}{{\mathtt{16}}}} = {\mathtt{6.187\: \!5}}$$
3.) 100 % -25 % = 75 % = 0,75 ; $${\mathtt{8.25}}{\mathtt{\,\times\,}}{\mathtt{0.75}} = {\frac{{\mathtt{99}}}{{\mathtt{16}}}} = {\mathtt{6.187\: \!5}}$$
Gruß radix 
!
+14538 
