Cost of a dozen pens (12 pens) = \(₹ 180\)∴ Cost of 1 pen = \(\frac{180}{12}\)= 15Cost of 8 ball pens =\( ₹ 56\)∴ Cost of 1 ball pen = \(\frac{56}{8}\)= 7Ratio of cost of one pen to that of one ball pen = \(\frac{15}{7}\)\(= 15:7\)