fracciones 6/5.1-3

Si es (6/5.1)-3, la respuesta es: $$\left({\frac{{\mathtt{6}}}{{\mathtt{5.1}}}}\right){\mathtt{\,-\,}}{\mathtt{3}} = {\mathtt{\,-\,}}{\frac{{\mathtt{31}}}{{\mathtt{17}}}} = -{\mathtt{1.823\: \!529\: \!411\: \!764\: \!705\: \!9}}$$

Si es 6/(5.1 - 3) : $${\frac{{\mathtt{6}}}{\left({\mathtt{5.1}}{\mathtt{\,-\,}}{\mathtt{3}}\right)}} = {\frac{{\mathtt{20}}}{{\mathtt{7}}}} = {\mathtt{2.857\: \!142\: \!857\: \!142\: \!857\: \!1}}$$

* Y la calculadora es útil:)  http://web2.0calc.com/