[tex]\frac{5}{8} - (-\frac{7}{8})[/tex]
Because of the double negative, this becomes [tex]\frac{5}{8} + \frac{7}{8}[/tex] which is [tex]\frac{5+7}{8}[/tex], and this is 12/8 or [tex]1\frac{1}{3}[/tex].