If a man earns 900% more than his original wage, it implies that the percentage of his original wage is 100% such that he earned 9 times his original wage. Thus 900/100 = 9
25/80 + 24/80 = 49/80. 16 and 20 both go into 80. !6 goes in 5 times so you multiply 5 by 5. 20 goes into 80 4 times so you multiply 4 by 4. 24/80 + 25/80 = 49/80.