5/8-x=5/3x (These are both fractions)
Is it possible your equation is
$\displaystyle \frac{5}{8 - x} = \frac{5}{3x}$?
If so, multiply both sides of the equation by $\displaystyle (8 - x) \cdot (3x)$ to get rid of those fractions. (And remind yourself at the end that x can't be either 0 nor 8.)
$\displaystyle 5(3x) = 5(8 - x)$ <-- Now divide both sides by 5
$\displaystyle 3x = 8 - x$
$\displaystyle 4x = 8$
$\displaystyle x = 2$
-Dan