we are told that the revenue is
this is a quadratic function, so to maximize it we should find the x-value of its vertex. recall that the x-value of the vertex of the parabola ax^2+bx+c is given by the formula −b/2a.
so in this case, we have a=−10 and b=4080, so the x-value of the vertex is
add -60 to 120 which will result in : 2x+3y=180
then subtract 2x: 3y=-2x+180
lastly, divide by 2: y= -2/3x+60
hope this is the answer you're looking for: )