Final answer:
The situation described is an example of barter, where individuals trade goods or services directly without the use of money.
Step-by-step explanation:
The situation described, where David and Asher buy the same pair of sneakers but in the wrong sizes and propose a size swap, is an example of barter. In barter, individuals trade goods or services directly without the use of money. In this case, David and Asher are exchanging sneakers, which have intrinsic value to both of them.