Answer:
We can calculate the difference between Lori's and Melissa's purse masses by subtracting Melissa's purse mass from Lori's purse mass:
Lori's purse mass = 16 ounces
Melissa's purse mass = 11 ounces
Difference = Lori's purse mass - Melissa's purse mass
Difference = 16 ounces - 11 ounces
Difference = 5 ounces
Therefore, the difference between Lori's and Melissa's purse masses is 5 ounces.