\(1-\dfrac{2}{7}-\dfrac{1}{4}=\dfrac{7}{7}-\dfrac{2}{7}=\dfrac{1}{4}=\dfrac{5}{7}-\dfrac{1}{4}=\dfrac{20}{28}-\dfrac{7}{28}=\dfrac{13}{28}\)
\(1-\dfrac{2}{7}-\dfrac{1}{4}=\dfrac{13}{28}\)
\(1-\dfrac{2}{7}-\dfrac{1}{4}=\dfrac{28}{28}-\dfrac{8}{28}-\dfrac{7}{28}=\dfrac{28-8-7}{28}=\dfrac{13}{28}\)
\(1-\dfrac{2}{7}-\dfrac{1}{4}=\dfrac{13}{28}\)