Thực hiện các phép tính: \(A = \dfrac{{ - 5}}{{12}} - 3:\dfrac{9}{4}\,\,;\,\,\)

* Hướng dẫn giải

\(\begin{array}{l}A = \dfrac{{ - 5}}{{12}} - 3:\dfrac{9}{4}\\\,\,\,\,\, = \dfrac{{ - 5}}{{12}} - 3.\dfrac{4}{9}\\\,\,\,\,\, = \dfrac{{ - 5}}{{12}} - \dfrac{4}{3}\\\,\,\,\, = \dfrac{{ - 5}}{{12}} - \dfrac{{16}}{{12}}\\\,\,\,\, = \dfrac{{ - 21}}{{12}} = \dfrac{{ - 7}}{4}\end{array}\)