The clock gains 16 minutes in 24 hours.
From 9:00 AM to 6:00 PM, the actual time elapsed is 9 hours.
The gain in 9 hours can be found using proportion:
Gain =24 hours16 minutes×9 hours
Gain =2416×9
Gain =24144
Gain =6 minutes
At actual 6:00 PM, the faulty clock will show:
Time shown =6:00 PM +6 minutes
Time shown =6:06 PM