$x=\dfrac{11}{13}+\dfrac{9}{17}+\dfrac{8}{15} \\ x-3=\dfrac{11}{13}-1+\dfrac{9}{17}-1+\dfrac{8}{15}-1 \\ x-3=-\dfrac{2}{13}-\dfrac{8}{17}-\dfrac{7}{15} \\ 3-x=\dfrac{2}{13}+\dfrac{8}{17}+\dfrac{7}{15} \\ \dfrac{4}{13}+\dfrac{16}{17}+\dfrac{14}{15}=6-2x$