\(a.\dfrac{3}{8}+\dfrac{-7}{12}+\dfrac{5}{6}=\dfrac{18-28+40}{48}=\dfrac{30}{48}=\dfrac{5}{8}.\)
\(b.\dfrac{3}{5}+\dfrac{4}{7}.\dfrac{14}{6}=\dfrac{3}{5}+\dfrac{4}{7}.\dfrac{7}{3}=\dfrac{3}{5}+\dfrac{4}{3}=\dfrac{29}{15}.\)
\(c.\dfrac{4}{5}+\dfrac{3}{5}:3-\dfrac{7}{8}=\dfrac{-3}{40}+\dfrac{1}{5}=\dfrac{1}{8}.\)
\(d.\left(\dfrac{5}{12}.\dfrac{21}{15}\right):\dfrac{1}{4}=\left(\dfrac{5}{12}.\dfrac{7}{5}\right).4=\dfrac{7}{12}.4=\dfrac{7}{3}.\)
\(e.\left(\dfrac{2}{3}+\dfrac{3}{4}\right).\left(\dfrac{5}{7}+\dfrac{5}{14}\right)=\dfrac{17}{12}.\dfrac{15}{14}=\dfrac{85}{56}.\)
\(f.\dfrac{18}{25}.\dfrac{1}{3^2}.5+\left(\dfrac{4}{5}+1\dfrac{2}{3}-\dfrac{3}{15}\right):\dfrac{-21}{10}.\\ =\dfrac{2}{5}+\dfrac{34}{15}:\dfrac{-21}{10}\\ =\dfrac{2}{5}-\dfrac{68}{63}=\dfrac{-214}{315}.\)
a: =9/24-14/24+20/24=15/24=5/8
b: =3/5+4/3=9/15+20/15=29/15
c: =4/5+1/5-7/8=1-7/8=1/8
d: =7/12x4=28/12=7/3
a: =9/24-14/24+20/24=15/24=5/8
b: =3/5+4/3=9/15+20/15=29/15
c: =4/5+1/5-7/8=1-7/8=1/8
d: =7/12x4=28/12=7/3