Question

when rearranging the equation 6y = 9 - 3x to make x the subject, am i right in thinking to add 3x to both sides (6y + 3x = 9), then subtract 6y on both sides(3x = 9 - 6y then divide both by 3(x = 9 - 6y/3)?

You have it.

x=3-2y