Two students did a problem as above, but one used x for the first variable and y for the secon variable and the other student used x for the second variable and y for the first variable. how did thier answers differ and which one, if either, was incorrect?

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.