The average weight of three men 'X'. T and 'Z' is 75 kg. Another man 'A joins the group and the average weight now becomes 80 kg. If another person 'B' whose weight is 5 kg more than 'A replaces 'X', then the average weight of T, 'Z', 'A and 'B' will be 85 kg. What is the weight of 'X'?