So one metric hour is one-tenth of a day, which means it is 2.4 hours (1/10*12).
1 metric minute is one-tenth of a metric hour, which means it is 2.4*1/10*60 = 14.4 minutes.
1 metric second is one-tenth of a metric minute, meaning it is 14.4*1/10*60 = 86.4 seconds.
All in all, then, 7:8:1 would be:
[tex]7*2.4:8*14.4:86.4[/tex]
[tex]16.8:115.2:86.4[/tex]
[tex]18:44:38.4[/tex]