8x + 2y = 2y + 8x. What is it?

Someone answer this check out the image!

Suppose that the price p, in dollars, and the number of sales, x, of a certain item follow the equation 4 p plus 4 x plus 2 pxequals56. suppose also that p and x are both functions of time, measured in days. find the rate at which x is changing when xequals2, pequals6, and startfraction dp over dt endfraction equals1.5.

The graph of a curve that passes the vertical line test is a: