The three numbers given in the question needs to be added to get to the desired result. So carefully looking at the information's given is of absolute necessity.
(1/6) + (2/3) + (1/4) = (2 + 8 + 3)/12
= 13/12
= 1 1/12
So the answer to the question is 1 1/12. I hope the procedure is clear enough for you to understand. Only be careful while finding the common multiple of the denominators 6, 3, 4. After that finding the result is very easy.