You need to subtract times.
If you need to borrow an hour, borrow and hour, and add 60 minutes to the minute part. Then subtract.
6:18 pm - 4:55 pm
Borrow 1 hour from the 6 hours leaving 5 hours.
The borrowed hour is 60 minutes.
Add the 60 minutes to the 18 minutes making 78 minutes.
Now you are subtracting 4:55 from 5:78.
Subtract 4 from 5 to give you hours.
Subtract 55 from 78 to give you minutes.
6:18 5:78
- 4:55 - 4:55
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1:23
Answer: You cooked for 1 hour and 23 minutes.