If Melissa has 16 stamps and 3/4 of them are from the United States, then the number of stamps from the United States is:
(3/4) x 16 = 12
To find the number of stamps that are not from the United States, we can subtract the number of stamps from the United States from the total number of stamps:
16 - 12 = 4
Therefore, Melissa has 12 stamps from the United States and 4 stamps that are not from the United States.