Answer: 5184.000 seconds
Explanation:
If there are 30 days per month then we are trying to find how many seconds the clock will gain in 180 days (30*6). If the clock gains 0.020 seconds per minute, then it gains 28.800 seconds per day (0.020*60*24). We can then multiply this by 180 days to get 5184.000 seconds.
