What is 5/12+1/4 equal to

(5/12)+(1/4)=(2/3)
To solve this without a calculator, you have to find a common denomintor: Here you can use 12 because 4 fits into twelve well. SO you extend (1/4) by multiplying it by (3/3). 3/3 is equal to one, so it doesn't change the value, but you end up with 3/12 which you can then add to the 5/12:
1.  5/12+1/4   > now multiply 1/4 by 3/3 as explained above
2.  5/12+3/12
3.  (5+3)/12      This is just rewritten what's standing in 2. with combining the numerators over the common denomintor
4.  8/12           
5.  2/3             you devide both the denominator and the numerator by 4 to simplify
And that's it ;) I hope that made sense and helped ;)