a)   \(\frac{7}{-25}+\frac{-8}{25}=\frac{-7}{25}+\frac{-8}{25}=\frac{(-7)+(-8)}{25}=\frac{-15}{25}=\frac{-3}{5}\)

b)   \(\frac{1}{6}+\frac{-5}{6}=\frac{1+(-5)}{6}=\frac{-4}{6}=\frac{-2}{3}\)

c)   \(\frac{6}{13}+\frac{-14}{39}=\frac{18}{39}+\frac{-14}{39}=\frac{18+(-14)}{39}=\frac{4}{39}\)

d) \(\frac{4}{5}+\frac{4}{-18}=\frac{4}{5}+\frac{-2}{9}=\frac{36}{45}+\frac{-10}{45}=\frac{36+(-10)}{45}=\frac{26}{45}\)