how do i work out
2/5x-6=12
your post shows how important it is to use brackets to avoid ambiguity.
do you mean
(2/5)x-6=12 ? or
2/(5x) - 6 = 12 ? or
2/(5x-6) = 12
in any case, cross-multiply and your fractions are gone.
then solve as a simple basic equation.