\(\dfrac{1}{6}+\dfrac{-5}{6}=\dfrac{1-5}{6}=\dfrac{-4}{6}=\dfrac{-2}{3}\\ \dfrac{6}{13}+\dfrac{-14}{39}=\dfrac{6.3-14}{39}=\dfrac{18-14}{39}=\dfrac{4}{39}\\ \dfrac{4}{5}+\dfrac{4}{-18}=\dfrac{4}{5}-\dfrac{2}{9}=\dfrac{4.9-2.5}{5.9}=\dfrac{36-10}{45}=\dfrac{26}{45}\\ \dfrac{7}{21}+\dfrac{9}{-36}=\dfrac{1}{3}-\dfrac{1}{4}=\dfrac{1.4-1.3}{4.3}=\dfrac{1}{12}\\ \dfrac{-12}{18}+\dfrac{-21}{35}=\dfrac{-2}{3}+\dfrac{-3}{5}=\dfrac{-2.5-3.3}{3.5}=\dfrac{-10-9}{15}=-\dfrac{19}{15}\\ \dfrac{-3}{21}+\dfrac{6}{42}=\dfrac{-3.2+6}{21.2}=\dfrac{0}{45}=0\)
\(-\dfrac{18}{24}+\dfrac{15}{21}=-\dfrac{3}{4}+\dfrac{5}{7}=\dfrac{-3.7+5.4}{4.7}=\dfrac{-21+20}{28}=-\dfrac{1}{28}\\ \dfrac{1}{6}+\dfrac{2}{5}=\dfrac{1.5+2.6}{6.5}=\dfrac{5+12}{30}=\dfrac{17}{30}\\ \dfrac{3}{5}+\dfrac{-7}{4}=\dfrac{3.4-7.5}{5.4}=\dfrac{12-35}{20}=-\dfrac{23}{20}\\ \left(-2\right)+\dfrac{-5}{8}=\dfrac{-2.8-5}{8}=\dfrac{-16-5}{8}=-\dfrac{21}{8}\\ \dfrac{1}{-8}+\dfrac{-5}{9}=\dfrac{-1.9-5.8}{8.9}=\dfrac{-9-40}{72}=\dfrac{-49}{72}\\ \dfrac{4}{13}+\dfrac{-\left(-12\right)}{39}=\dfrac{4}{13}+\dfrac{12}{39}=\dfrac{4}{13}+\dfrac{4}{13}=\dfrac{8}{13}\)
\(\dfrac{-\left(-1\right)}{21}+\dfrac{1}{28}=\dfrac{1}{21}+\dfrac{1}{28}=\dfrac{1.4+1.3}{84}=\dfrac{7}{84}=\dfrac{1}{12}\\ -\dfrac{3}{29}+\dfrac{16}{58}=\dfrac{-3.2+16}{58}=\dfrac{-6+16}{58}=\dfrac{10}{58}=\dfrac{5}{29}\\ \dfrac{8}{40}+\dfrac{-36}{45}=\dfrac{1}{5}-\dfrac{4}{5}=\dfrac{1-4}{5}=-\dfrac{3}{5}\\ \dfrac{-8}{18}+\dfrac{-15}{27}=\dfrac{-4}{9}+\dfrac{-5}{9}=\dfrac{-4-5}{9}=\dfrac{-9}{9}=-1\)
\(\dfrac{13}{30}+\dfrac{-1}{5}=\dfrac{13-1.6}{30}=\dfrac{13-6}{30}=\dfrac{7}{30}\\ \dfrac{2}{21}+\dfrac{1}{28}=\dfrac{2.4+1.3}{84}=\dfrac{8+3}{84}=\dfrac{11}{84}\\ 5+\dfrac{-3}{4}=\dfrac{5.4-3}{4}=\dfrac{20-3}{4}=\dfrac{17}{4}\\ \dfrac{18}{24}+\dfrac{35}{-10}=\dfrac{3}{4}-\dfrac{7}{2}=\dfrac{3-7.2}{4}=\dfrac{3-14}{4}=\dfrac{-11}{4}\)
