4/5 - (-2/7) - 7/10
= 4/5 + 2/7 - 7/10
= 8/10 - 7/10 + 2/7
= 1/10 + 2/7
= 7/70 + 20/70
= 27/70
\(\dfrac{4}{5}-\left(-\dfrac{2}{7}\right)-\dfrac{7}{10}\)
\(=\dfrac{4}{5}+\dfrac{2}{7}-\dfrac{7}{10}\)
\(=\dfrac{8-7}{10}+\dfrac{2}{7}\)
\(=\dfrac{1}{10}+\dfrac{2}{7}\)
\(=\dfrac{7+20}{70}\)
\(=\dfrac{27}{70}\)