Question

If the cooking time is 4.33 hours and the food should be ready by 17:15pm what time should we start cooking

Answer 1

17: 15 is 5:15 so 5:15 minus the cooking time 4.33 = 1:18, so you start cooking at 1:18.

Answer 2

for this purpose we will separate the hours from given time
the time at which cooking started =17:15  - 4 .33
= 12 .82 pm is the answer...
in other way 17 : 15 is 5:15 when we subtract 4. 33 from it it will be 0: 82 means 12:82 pm...