Question

How to find a

Answer 1

Find the multiples of each denominator
In this case...
It would be 4, 8, 12
12

See when you come to a common number

(3×3)/(4×3) to get 12 + (5×1)/(12×1) whatever u do to the bottom do to the top
9/12 + 5/12
14/12
7/6

Answer 2

In reality your common denominator should be the Least Common Multiple. The LCM is the product of highest occurring primes of the numbers prime factorizations...

4=2*2, and 12=2*2*3.  So the LCM is 2*2*3=12  Now that you know what the least common multiple is we can say that:

(3/4)(3/3)+5/12

9/12+5/12

(9+5)/12

14/12

7/6  which should be converted to a mixed number as this is an improper fraction...

(6+1)/6

1+1/6

1 1/6