In this equation 0/y would equal 0, no matter what y is. 0/y means that there's 0 items out of y items (ex: substitute y with 2, it would be 0/2). Beginning with 1*0 (one times zero) the answer there would be 0. Since we already know that 0/y equals 0, the rest of the equation would be 0 - 0 which would equal to 0. Hope this explanation helps :)
