b) (-2/3 + 4/5) - 5/4( -16/3) -11/5 .

b) $\left(\frac{-2}{3}+\frac{4}{5}\right)-\frac{5}{4}.\left(-\frac{16}{3}\right)+\frac{11}{5}$

$=\frac{-2}{3}+\frac{4}{5}+\frac{5}{4}.\frac{16}{3}+\frac{11}{5}$

$=\frac{-2}{3}+\frac{4}{5}+\frac{5}{1}.\frac{4}{3}+\frac{11}{5}$

$=\frac{-2}{3}+\frac{4}{5}+\frac{20}{3}+\frac{11}{5}$

$=\left(\frac{-2}{3}+\frac{20}{3}\right)+\left(\frac{4}{5}+\frac{11}{5}\right)$

$=\frac{18}{3}+\frac{15}{5}$

= 6 + 3

= 9.

Vậy biểu thức đã cho có giá trị bằng 9.