a)12.(\(\frac{-5}{3}+\frac{7}{4}\) ) \(-16\left[\left(\frac{-1}{2}\right)^2-\left(\frac{-5}{2}\right)^3\right]\)
=-20+21-4-1000
=-1005
b)\(\frac{-3}{4}:\left(\frac{1}{2}+\frac{-2}{3}\right)-\frac{16}{25}\)
=\(\frac{-3}{4}:\frac{-1}{6}-\frac{4}{5}\)
=\(\frac{9}{2}-\frac{4}{5}\)
=\(\frac{37}{10}\)