You have to make them have their least common denominator to add or subtract, in this case 36.
Multiply 1/12 by 3, to get the denominator 36: 3/36.
Multiply 7/9 by 4, to get the denominator 36: 28/36.
Now add the numerators: 3+28=31, 31/36 is as simplified as possible so your answer is 31/36 :) I hope this helps :)
