Answer
$\frac{1}{10}$
Work Step by Step
We need a common denominator (bottom of the fraction) to subtract the numerators (tops of the fractions). Thus, we multiply $\frac{4}{5}$ by $\frac{2}{2}$ to get $\frac{8}{10}$. (This is legal because $\frac{2}{2}$ is equal to one).
We now have:
$\frac{9}{10}$-$\frac{8}{10}$
Because we have the same denominators, we can subtract the numerators to obtain:
$\frac{1}{10}$
