Istarted cooking at4: 55 pm i finish cooking at 6: 18 pm how long did i cook

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
         
                         1:23

You cooked for 1 hour and 23 minutes.