Answer:
=3 + 4/12 + 3/12
Explanation:
To make 1/3 into a twelfth, you have to multiply the 3 by 4 to get 12. Whatever you do to the top you have to do to the bottom, meaning that you have to multiply 1 by 4 to get 4 on top.
To make 1/4 into a twelfth, you have to multiply the 4 by 3 to get 12. Whatever you do to the top you have to do to the bottom, meaning that you have to multiply 1 by 3 to get 3 on top.