b page that linking to web page A.???C??? is a number of out bound link that page t1 and tn.???D??? is damping factor normally 0.85.In the equation 't1 - tn' are pages linking to page A, 'C' is the number of outbound links that a page has and 'd' is a damping factor, usually set to 0.85.Page Rank use to define how important web page on the web.