Answer
$\displaystyle \frac{7}{3x}$
Work Step by Step
To add rational expressions with the same denominator,
add numerators and place the sum over the common denominator.
If possible, factor and simplify the result.
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$\displaystyle \frac{8}{9x}+\frac{13}{9x} = \displaystyle \frac{8+13}{9x}$
$= \displaystyle \frac{21}{9x}$
$= \displaystyle \frac{3(7)}{3(3x)}\qquad$... reduce by 3
= $\displaystyle \frac{7}{3x}$
