\(a,\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{9}{15}-\dfrac{5}{15}=\dfrac{4}{15}\)
\(b,\dfrac{1}{12}+\dfrac{1}{6}+\dfrac{1}{4}=\dfrac{1}{12}+\dfrac{2}{12}+\dfrac{3}{12}=\dfrac{6}{12}=\dfrac{1}{2}\)
\(c,\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{23}+\dfrac{1}{6}=\left(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}\right)+\dfrac{1}{23}=\left(\dfrac{3}{6}+\dfrac{2}{6}+\dfrac{1}{6}\right)+\dfrac{1}{23}\)
\(=1+\dfrac{1}{23}=\dfrac{24}{23}\)
\(A,=\dfrac{9}{15}+\dfrac{-5}{15}=\dfrac{4}{15}\)
\(B,=\dfrac{1}{12}-\left(-\dfrac{4}{24}-\dfrac{6}{24}\right)=\dfrac{1}{12}-\dfrac{-5}{12}=-\dfrac{1}{3}\)
\(C,=\dfrac{1}{6}+\dfrac{1}{23}+\dfrac{1}{6}=\left(\dfrac{1}{6}+\dfrac{1}{6}\right)+\dfrac{1}{23}=\dfrac{1}{3}+\dfrac{1}{23}=\dfrac{26}{69}\)