Answer:18/12 or 1 1/2
Explanation:
First you have to make all of the denominators the same by finding a common denominator which is 12. Then you multiply the whatever number you need to get to twelve by the top and bottom. Once all of the denominators are the same then you add.
1/4=3/12(multiply top and bottom by three), 1/3=4/12(multiply by 4), 11/12 stays the same.