Tính các phép tính: (a) 25 3/19 . − 4/5 − 35 3/19 . − 4/5 .

a) \(25\frac{3}{{19}}.\frac{{ - 4}}{5} - 35\frac{3}{{19}}.\frac{{ - 4}}{5} = \frac{{ - 4}}{5}.\left( {25\frac{3}{{19}} - 35\frac{3}{{19}}.} \right)\)

\( = \frac{{ - 4}}{5}.( - 10) = 8\)

b) \(5:{\left( {\frac{{ - 5}}{2}} \right)^2} + \frac{2}{{15}}.\sqrt {\frac{{25}}{4}} - {2023^0} + 0.5 = 5:\frac{{25}}{4} + \frac{2}{{15}}.\frac{5}{2} - 1 + \frac{1}{2}\)

\( = \frac{4}{5} + \frac{1}{3} - 1 + \frac{1}{2} = \frac{{24}}{{30}} + \frac{{10}}{{30}} - \frac{{30}}{{30}} + \frac{{15}}{{30}} = \frac{{19}}{{30}}\)