[tex]( - \frac{3}{7}) + ( + \frac{5}{8}) + ( - \frac{8}{24}) + ( + \frac{9}{14}) = - \frac{3}{7} + \frac{5}{8} - \frac{8}{24} + \frac{9}{24} = - \frac{3}{7} + \frac{5}{8} - \frac{1}{3} + \frac{3}{8} = \frac{ - 72 + 105 - 56 + 63}{168} = \frac{40}{168} = \frac{5}{21} [/tex]
