From 8:58 to 12:30 how many hours did i work

You worked 5hrs & 2mins. approximately?

From 8:58 to 9:00, there is 2 minutes.

From 9:00 to 12:00 there is 3 hours.

From 12:00 to 12:30 there is 30 minutes.

So therefore you worked 3 hours and 32 minutes. Technically, you can round it to closer to 4 hours.