\(6-\left(\dfrac{15}{28}-\dfrac{4}{14}\right)\\ =6-\left(\dfrac{15}{28}-\dfrac{2}{7}\right)\\ =6-\left(\dfrac{15}{28}-\dfrac{8}{28}\right)\\ =6-\dfrac{7}{28}\\ =6-\dfrac{1}{4}\\ =\dfrac{24}{4}-\dfrac{1}{4}\\ =\dfrac{23}{4}\)
=6-15/28+4/14
=168/28-15/28+8/28
=161/28=23/4
\(c,6-\left(\dfrac{15}{28}-\dfrac{4}{14}\right)\\ =6-\left(\dfrac{15}{28}-\dfrac{8}{28}\right)\\ =6-\dfrac{1}{4}\\ =\dfrac{24}{4}-\dfrac{1}{4}=\dfrac{23}{4}\)