\(a,=-\dfrac{4}{15}+\dfrac{3}{2}=\dfrac{37}{30}\\ b,=\dfrac{6}{5}:\dfrac{8}{6}-\dfrac{9}{16}+\dfrac{1}{4}=\dfrac{9}{10}-\dfrac{9}{16}+\dfrac{1}{4}=\dfrac{47}{80}\\ c,=-\dfrac{7}{2}\left(25\dfrac{1}{9}-15\dfrac{1}{9}\right)=-\dfrac{7}{2}\cdot10\dfrac{1}{9}=-\dfrac{7}{2}\cdot\dfrac{91}{9}=-\dfrac{637}{18}\)