\(a,A=\dfrac{-1}{8}+\dfrac{5}{8}=\dfrac{4}{8}=\dfrac{1}{2}\\ b,B=\dfrac{3}{5}.\dfrac{5}{4}-\dfrac{3}{5}.\dfrac{1}{4}=\dfrac{3}{5}\left(\dfrac{5}{4}-\dfrac{1}{4}\right)=\dfrac{3}{5}.\dfrac{4}{4}=\dfrac{3}{5}.1=\dfrac{3}{5}\\ c,\dfrac{34}{19}+\dfrac{-7}{15}+\dfrac{-8}{15}-\dfrac{15}{19}=\left(\dfrac{34}{19}-\dfrac{15}{19}\right)+\left(\dfrac{-7}{15}+\dfrac{-8}{15}\right)=\dfrac{19}{19}+\dfrac{-15}{15}=1+\left(-1\right)=0\\ d,D=5\dfrac{3}{7}-\left(4\dfrac{3}{7}+1\right)=\left(5\dfrac{3}{7}-4\dfrac{3}{7}\right)-1=1-1=0\)
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