To anwer this question we need to remember that:
[tex]\frac{a}{b}+\frac{c}{d}=\frac{ad+bc}{bd}[/tex]With this in mind, let's make the operation:
[tex]-\frac{1}{8}+\frac{9}{10}=\frac{-10+72}{80}=\frac{62}{80}=\frac{31}{40}[/tex]Therefore the answer is 31/40
