To solve this problem, we need to find a common denominator for 5/8 and 3/12.
The prime factorization of 8 is 2 x 2 x 2, and the prime factorization of 12 is 2 x 2 x 3.
A common denominator for 5/8 and 3/12 is the least common multiple (LCM) of 8 and 12, which is 24 (2 x 2 x 2 x 3).
We can convert both fractions to have a denominator of 24 as follows:
5/8 = (5/8) x (3/3) x (3/3) = 15/24
3/12 = (3/12) x (2/2) x (4/4) = 6/24
Now we can add the fractions:
15/24 + 6/24 = 21/24
We can simplify this fraction by dividing both the numerator and denominator by their greatest common factor, which is 3:
21/24 = (21/3) / (24/3) = 7/8
Therefore, 5/8 + 3/12 = 7/8.
The answer is (B) 7/8.