\(a,=\dfrac{25}{28}.\dfrac{7}{9}.\dfrac{9}{7}\\ =\dfrac{25}{28}\\ b=\dfrac{4}{7}.\dfrac{7}{4}.\dfrac{17}{8}.\dfrac{18}{7}\\ =\dfrac{17}{8}.\dfrac{18}{7}=\dfrac{153}{28}\)
\(\dfrac{7}{9}\cdot\dfrac{25}{28}\cdot\dfrac{9}{7}=\left(\dfrac{7}{9}\cdot\dfrac{9}{7}\right)\cdot\dfrac{25}{28}=1\cdot\dfrac{25}{28}=\dfrac{25}{28}\)
\(\dfrac{4}{7}\cdot\dfrac{17}{8}\cdot\dfrac{7}{4}\cdot\dfrac{18}{7}=\left(\dfrac{4}{7}\cdot\dfrac{7}{4}\right)\cdot\left(\dfrac{17}{8}\cdot\dfrac{18}{7}\right)=1\cdot\dfrac{153}{28}=\dfrac{153}{28}\)
\(\dfrac{7}{9}.\dfrac{25}{28}.\dfrac{9}{7}\)
=\(\dfrac{7}{9}.\dfrac{9}{7}.\dfrac{25}{28}\)
=1.\(\dfrac{25}{28}\)
=\(\dfrac{25}{28}\)
b,\(\dfrac{4}{7}.\dfrac{17}{8}.\dfrac{7}{4}.\dfrac{18}{7}\)
=\(\dfrac{4}{7}.\dfrac{7}{4}.\dfrac{17}{8}.\dfrac{18}{7}\)
=1.\(\dfrac{17}{8}.\dfrac{18}{7}\)
=\(\dfrac{17}{8}.\dfrac{18}{7}\)
=\(\dfrac{153}{28}\)
7/9x25/28x9/7=(7/9x9/7)x25/28=1x25/28=25/28
4/7x17/8x7/4x18/7
=(4/7x7/4)x(17/8x18/7)
=1x[(17/2x4)x(2x9/7)]
=1x(17/4x9/7)
=1x153/28
=153/28
