Answer:
Myron would need 7.2 hours to cook 3 kilograms of meat. 
Explanation:
We have,
Myron takes 12 hours to cook 5 kilograms of meat.
i.e. For 5 kilograms of meat, he takes 12 hours to cook.
Thus, for 3 kilograms of meat, he will need 
 i.e.
 i.e. 
 i.e.
 i.e. 
 i.e. 7.2 hours
 i.e. 7.2 hours
Hence, we get that,
Myron would need 7.2 hours to cook 3 kilograms of meat.