1)
\(\dfrac{-3}{14}+\dfrac{2}{13}+\dfrac{-25}{14}+\dfrac{-15}{13}\\ =\left(\dfrac{-3}{14}+\dfrac{-25}{14}\right)+\left(\dfrac{2}{13}+\dfrac{-15}{13}\right)\\ =\dfrac{-28}{14}+\dfrac{-13}{13}\\ =-2-1\\ =-3\)
2)
\(\dfrac{14}{13}+\left(\dfrac{-1}{13}-\dfrac{19}{20}\right)\\ =\dfrac{14}{13}-\dfrac{1}{13}-\dfrac{19}{20}\\ =\dfrac{13}{13}-\dfrac{19}{20}\\ =1-\dfrac{19}{20}\\ =\dfrac{1}{20}\)
3)
\(\dfrac{17}{28}\cdot\dfrac{-5}{18}+\dfrac{17}{28}\cdot\dfrac{-13}{18}\\ =\dfrac{17}{28}\cdot\left(\dfrac{-5}{18}+\dfrac{-13}{18}\right)\\ =\dfrac{17}{28}\cdot\dfrac{-18}{18}\\ =-\dfrac{17}{28}\)
4) \(\dfrac{-24}{17}-\left(\dfrac{-7}{17}-\dfrac{1}{16}\right)\)
\(=\dfrac{-24}{17}+\dfrac{7}{17}+\dfrac{1}{16}\)
\(=\dfrac{-17}{17}+\dfrac{1}{16}\)
\(=-1+\dfrac{1}{16}\)
\(=\dfrac{-15}{16}\)
5)
\(\dfrac{21}{25}\cdot\dfrac{11}{9}\cdot\dfrac{5}{7}\\ =\dfrac{3\cdot7\cdot11\cdot5}{5^2\cdot3^2\cdot7}\\ =\dfrac{11}{5\cdot3}\\ =\dfrac{11}{15}\)
