The smallest of the fractions among 5/8, 3/4, 13/16, 7/12 is

5/8 = 0.625

3/4 = 0.75

13/16 = 0.8125

7/12 = 0.583

Smallest fraction = 7/12.

Or else convert all the denominators into a common denominator by taking LCM of all numbers.

Here the numbers are 8,4,16 and 12. So, LCM of these numbers = 48.

So we will get $$ \frac {5}{8} \times \frac {6}{6}, \frac {3}{4} \times \frac {12}{12}, \frac {13}{16} \times \frac {3}{3}, \frac {7}{12} \times \frac {4}{4}$$

= $$ \frac {30}{48}, \frac {36}{48}, \frac {39}{48}, \frac {28}{48}$$

Hence clearly the smallest fraction is the one having the smallest numerator.

Hence 7/12 is the answer.