What the missing number for clclxx cxc ccx?

To find the missing number in the sequence "clclxx cxc ccx," we first convert the Roman numerals to Arabic numerals. "clclxx" represents 170, "cxc" represents 190, and "ccx" represents 210. The numbers increase by 20 each time, so the missing number between 170 and 190 is 180. Therefore, the missing number is 180.