\(a,=\dfrac{4}{7}-\dfrac{1}{8}-\dfrac{4}{7}-\dfrac{7}{8}=-1\\ b,=\dfrac{9}{2}\left(-\dfrac{1}{3}+\dfrac{2}{5}-\dfrac{2}{3}+\dfrac{8}{5}\right)=\dfrac{9}{2}\left(-1+2\right)=\dfrac{9}{2}\\ c,=\dfrac{2^5.3^{10}.5^4}{3^8.3^3.5^3.2^2.5^2}=\dfrac{2^3}{3.5}=\dfrac{8}{15}\)