The blame should be put squarely on the shoulders of tophatter.com. They know the quality of what is being sold and choose to look the other way for the sake of making commission and sales fees on these imitation goods. In my estimation and also the interpretation of the law this is outright FRAUD.
Inverse operations are opposite operations that undo each other. Addition and subtraction are inverse operations. Multiplication and division are inverse operations.
Addition and subtraction concepts have been developed through hands-on experiences with countable objects or place value blocks. Addition is the putting together of two groups of objects and finding how many in all. Subtraction tells how many are left or how many more or less.. We say addition and subtraction are inverse operations because one operation can undo the other operation. Adding 3 and 5 to get 8 is the opposite of 8 minus 5, leaving 3. 3+5=8 and 85=3 addends sum difference.