Thực hiện phép tính :a) (75\%  - 1frac{1}{2} + 0,5:frac{5}{{12}})b) ( - 1frac{1}{4}.

a) \(75\%  - 1\frac{1}{2} + 0,5:\frac{5}{{12}}\)

\(\begin{array}{l}

 = \frac{3}{4} - \frac{3}{2} + \frac{1}{2}:\frac{5}{{12}}\\
 = \frac{3}{4} - \frac{3}{2} + \frac{6}{5}\\
 = \frac{{15}}{{20}} - \frac{{30}}{{20}} + \frac{{24}}{{20}} = \frac{9}{{20}}
\end{array}\)

b) \( - 1\frac{1}{4}.\frac{{{{( - 2)}^2}}}{5} + \frac{1}{5}:2\)

\(\begin{array}{l}
 = \frac{{ - 5}}{4}.\frac{4}{5} + \frac{1}{5}.\frac{1}{2} = ( - 1) + \frac{1}{{10}}\\
 = \frac{{ - 10}}{{10}} + \frac{1}{{10}} = \frac{{ - 9}}{{10}}
\end{array}\)