a)\(-\frac{5}{13}:\left(\frac{145}{28}-\frac{17}{9}.\frac{5}{4}+\frac{79}{63}\right)\)
\(=-\frac{5}{13}:\left(\frac{145}{28}-\frac{85}{36}+\frac{79}{63}\right)\)
\(=-\frac{5}{13}:\left(\frac{145}{28}-\frac{31}{28}\right)\)
\(=-\frac{5}{13}:\frac{57}{14}\)
\(=-\frac{70}{741}\)