Question

Answer 1

\(a,\left(\dfrac{-7}{15}-\dfrac{27}{70}\right)-\left(\dfrac{8}{15}+\dfrac{43}{70}\right).\\ =\dfrac{-7}{15}-\dfrac{27}{70}-\dfrac{8}{15}-\dfrac{43}{70}.\\ =\left(\dfrac{-7}{15}-\dfrac{8}{15}\right)-\left(\dfrac{27}{70}+\dfrac{43}{70}\right).\\ =-1-1=-2.\)

\(b,\dfrac{3}{7}+\left(\dfrac{-1}{5}+\dfrac{-3}{7}\right).\\ =\dfrac{3}{7}+\dfrac{-1}{5}+\dfrac{-3}{7}.\\ =0+\dfrac{-1}{5}=-\dfrac{1}{5}.\\ c,\left(4-\dfrac{12}{5}\right).\dfrac{25}{8}-\dfrac{2}{5}:\dfrac{-4}{25}.\\ =\dfrac{25}{2}-\dfrac{15}{2}+\dfrac{5}{2}.\\ =5+\dfrac{5}{2}=\dfrac{15}{2}.\)