a) \(\dfrac{4}{7}+\dfrac{3}{4}+\dfrac{2}{7}+\dfrac{5}{4}+\dfrac{1}{7}=\left(\dfrac{4}{7}+\dfrac{2}{7}+\dfrac{1}{7}\right)+\left(\dfrac{3}{4}+\dfrac{5}{4}\right)=1+2=3\)
b) \(-\dfrac{5}{7}+\dfrac{3}{4}+-\dfrac{1}{5}+-\dfrac{2}{7}+\dfrac{1}{4}=\left[\left(-\dfrac{5}{7}\right)+\left(-\dfrac{2}{7}\right)\right]+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+-\dfrac{1}{5}=\left(-1\right)+1+\left(-\dfrac{1}{5}\right)=\left(-\dfrac{1}{5}\right)\)
c) \(\dfrac{5}{13}+\dfrac{-5}{7}+-\dfrac{20}{41}+\dfrac{8}{13}+-\dfrac{21}{41}=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left[\left(-\dfrac{20}{41}\right)+\left(-\dfrac{21}{41}\right)\right]+\left(-\dfrac{5}{7}\right)=1+\left(-1\right)+\left(-\dfrac{5}{7}\right)=\left(-\dfrac{5}{7}\right)\)
d) \(\dfrac{1}{28}+\left(-\dfrac{1}{14}\right)+\dfrac{3}{28}+\left(-\dfrac{1}{7}\right)+\dfrac{3}{14}=\left(\dfrac{1}{28}+\dfrac{3}{28}\right)+\left[\left(-\dfrac{1}{14}\right)+\dfrac{3}{14}\right]+\left(-\dfrac{1}{7}\right)=\dfrac{1}{7}+\dfrac{1}{7}+\left(-\dfrac{1}{7}\right)=\dfrac{1}{7}\)
