The additional yards of burlap that Jim needs to purchase to cover his bulletin board may be calculated by subtracting the 1 1/6 from 3 1/2. To solve mixed fractions, convert them first to improper fractions,
7/2 - 7/6 = 7/3.
The improper fraction 7/3 is equal to 2 1/3. Thus, Jim needs to purchase 2 1/3 more of the burlap.