The amount recenue in dollars, y, that jason receives from selling x posters is given by the equation y=4x. the cost of producing x posters is given by the equation y=1/2x+280. how many posters does jason need to sell so that the cost and revenue are equal?

For this case we have the following equations:
 revenue: y = 4x
 cost: y = 1 / 2x + 280
 We must match both equations:
 4x = 1 / 2x + 280
 From here, we clear the value of x:
 4x-1 / 2x = 280
 7 / 2x = 280
 x = (2/7) * (280)
 x = 80
 
 jason needs to sell 80 posters so that the cost and revenue are equal