Réponse:
[tex]a = \frac{ \frac{2}{5} - \frac{4}{3} }{3 + \frac{ - 5}{6} } - \frac{4}{5} = \frac{ \frac{2 \times 3}{5 \times 3} - \frac{4 \times 5}{3 \times 5} }{ \frac{3 \times 6}{6} + \frac{ - 5}{6} } - \frac{4}{5} = \frac{ \frac{6}{15} - \frac{20}{15} }{ \frac{18}{6} + \frac{ - 5}{6} } - \frac{4}{5} = \frac{ \frac{ - 14}{15} }{ \frac{13}{6} } - \frac{4}{5} = \frac{ \frac{ - 84}{90} }{ \frac{195}{90} } - \frac{4}{5} = \frac{-84\times 90}{90 \times 195} - \frac{4}{5} = \frac{-7560}{17550} - \frac{4}{5} = \frac{-7560÷270}{17550÷270}-\frac{4}{5} = \frac{-28}{65} - \frac{4×13}{5×13} = \frac{-28}{65} - \frac{52}{65} = \frac{-80}{65}[/tex]
