\(\dfrac{4}{5}:-\dfrac{2}{7}-\dfrac{9}{5}:-\dfrac{2}{7}-\left(-1\right)^{2020}\)
\(=\dfrac{4}{5}.\dfrac{-7}{2}-\dfrac{9}{5}.\dfrac{-7}{2}-1\)
\(=-\dfrac{7}{2}\left(\dfrac{4}{5}-\dfrac{9}{5}\right)-1\)
\(=-\dfrac{7}{2}.\left(-1\right)-1\)
\(=\dfrac{7}{2}-\dfrac{2}{2}=\dfrac{5}{2}\)
\(\dfrac{4}{5}:\dfrac{-2}{7}-\dfrac{9}{5}:\dfrac{-2}{7}-\left(-1\right)^{2020}=\dfrac{-2}{7}:\left(\dfrac{4}{5}-\dfrac{9}{5}\right)-1=\dfrac{-2}{7}:\left(-1\right)-1=\dfrac{-2}{7}.\dfrac{-1}{1}-1=\dfrac{2}{7}-1=\dfrac{-5}{7}\)
`4/5:(-2)/7 - 9/5:(-2)/7 - (-1)^2020`
`=4/5 . (-7)/2 - 9/5.(-7)/2 - 1`
`=-7/2 . (4/5-9/5)-1`
`=-7/2 . (-5/5)-1`
`=-7/2 . (-1)-1`
`=7/2.1-1`
`=7/2-1`
`=7/2-2/2`
`=5/2`
