\[\boxed{\text{5.\ 19}}\]
\[\textbf{а)}\ A = \frac{- 7 + 9}{2} = \frac{2}{2} = 1.\]
\[\textbf{б)}\ A = \frac{- 4 + 3}{2} = - \frac{1}{2} = - 0,5.\]
\[\textbf{в)}\ A = \frac{- 5,5 + 2\frac{1}{2}}{2} =\]
\[= \frac{- 5,5 + 2,5}{2} = - \frac{3}{2} = - 1,5.\]
\[\textbf{г)}\ A = \frac{- 7 - 1\frac{1}{5}}{2} = \frac{- 7 - 1,2}{2} =\]
\[= - \frac{8,2}{2} = - 4,1.\]