Since the equation is parallel to y=2x-4 that means they have the same slope. Now that you have the slope and fortunately a point, you can solve this by using point slope formula
Which is what I did on the attached picture and just rearrange it after solving to Ax+By=C/2x-y=6
Which is what I did on the attached picture and just rearrange it after solving to Ax+By=C/2x-y=6