\[\boxed{\text{5.\ 3}}\]
\[\textbf{а)} - ( - 3,48 + 2,13) =\]
\[= - ( - 1,35) = 1,35\]
\[\textbf{б)} - (8,29 - 4,56) = - 3,73\]
\[\textbf{в)} - \left( - \frac{5}{9} - \frac{1}{3} \right) = \frac{5}{9} + \frac{3}{9} = \frac{8}{9}\]