`a)`
`7/8 : ( 14/3 + 7/2) + 4/28`
`=7/8 : 49/6 + 4/28`
`= 7/8 xx 6/49 + 4/28`
`= 3/28 + 4/28`
`= 7/28=1/4`
`b)`
`(6- 14/5 ) xx 25/8 + 18/5 : 1/20`
`= 16/5 xx 25/8 + 18/5 xx 20`
`= 10 + 72`
`=82`
a \(\dfrac{7}{8}:\dfrac{49}{6}+\dfrac{4}{28}=\dfrac{7}{8}\times\dfrac{6}{49}+\dfrac{4}{28}=\dfrac{3}{28}+\dfrac{4}{28}=\dfrac{7}{28}=\dfrac{1}{4}\)
b \(\dfrac{16}{5}\times\dfrac{25}{8}+\dfrac{18}{5}\times20=10+72=82\)
\(a,\dfrac{7}{8}:\left(\dfrac{14}{3}+\dfrac{7}{2}\right)+\dfrac{4}{28}=\dfrac{7}{8}:\left(\dfrac{28}{6}+\dfrac{21}{6}\right)+\dfrac{1}{7}=\dfrac{7}{8}:\dfrac{49}{6}+\dfrac{1}{7}=\dfrac{7}{8}\times\dfrac{6}{49}+\dfrac{1}{7}=\dfrac{3}{28}+\dfrac{1}{7}=\dfrac{3}{28}+\dfrac{4}{28}=\dfrac{7}{28}=\dfrac{1}{4}\)
\(\left(6-\dfrac{14}{5}\right)\times\dfrac{25}{8}+\dfrac{18}{5}:\dfrac{1}{20}=\left(\dfrac{30}{5}-\dfrac{14}{5}\right)\times\dfrac{25}{8}+\dfrac{18}{5}\times\dfrac{20}{1}=\dfrac{16}{5}\times\dfrac{25}{8}+72=10+72=82\)
4 và 5