The answer in simplest form would be: 3/4
First, think of a common denominator: 12.
Multiply 1/4 by 3/3 (you need to do the same to top and bottom): 1/4x3/3=3/12
Multiply 3/6 by 2/2: 3/6x2/2=6/12
Then you just add the numerators together: 3/12+6/12 (3+6=9)
You don't need to add the denominators.
So the answer is 9/12. But you can simplify 9/12 to 3/4.
Hope this helps! :D