\(a,=-\dfrac{3}{21}-\dfrac{2.3}{21}\\ =\dfrac{-3-6}{21}=-\dfrac{3}{7}\\ b,=\dfrac{-13.6-5.5}{90}\\ =\dfrac{-103}{90}\\ c,=\dfrac{-2.\left(-7\right)}{12}\\ =\dfrac{14}{12}=\dfrac{7}{6}\\ d,=\left(-\dfrac{3}{25}\right).\dfrac{1}{6}\\ =\dfrac{-3}{25.6}=\dfrac{-1}{50}\)
a: =-1/7-2/7=-3/7
b: =-78/90-25/90=-103/90
c: =2x7/12=7/6
d: =-3/25x1/6=-3/150=-1/50
a,\(\dfrac{-3}{21}+\dfrac{-2}{7}=\dfrac{-1}{7}+\dfrac{-2}{7}=\dfrac{-3}{7}\)
b,\(\dfrac{-13}{15}+\dfrac{5}{18}=\dfrac{-78}{90}+\dfrac{25}{90}=\dfrac{-53}{90}\)
c,\(\left(-2\right).\left(\dfrac{-7}{12}\right)=\dfrac{14}{12}=\dfrac{7}{6}\)
d,\(\dfrac{-3}{25}:6=\dfrac{-1}{50}\)
