Question

Answer 1

\(-\dfrac{3}{7}+\dfrac{1}{13}=\dfrac{-39}{91}+\dfrac{7}{13}=-\dfrac{32}{91}\)

\(-\dfrac{7}{21}+\dfrac{8}{24}=-\dfrac{1}{3}+\dfrac{1}{3}=0\)

Answer 2

a) \(\dfrac{-3}{7}+\dfrac{5}{13}+\dfrac{-4}{13}=\dfrac{-3}{7}+\left(\dfrac{5}{13}+\dfrac{-4}{13}\right)=\dfrac{-3}{7}+\dfrac{1}{13}=\dfrac{-39}{91}+\dfrac{7}{91}=\dfrac{-32}{91}\)

b) \(\dfrac{-5}{21}+\dfrac{-2}{21}+\dfrac{8}{24}=\dfrac{-5}{21}+\dfrac{-2}{21}+\dfrac{1}{3}=\left(\dfrac{-5}{21}+\dfrac{-2}{21}\right)+\dfrac{1}{3}=\dfrac{-1}{3}+\dfrac{1}{3}=\dfrac{0}{3}=0\)