Answer:
an algorithm
Step-by-step explanation:
An algorithm as a problem solving strategy could be defined as a process or set of rules to be followed in a problem-solving operation.
In the example, Dennis "systematically" searches through his folders from A to Z for his missing receipt. Dennis's decision to search alphabetically in an organized manner shows he has set predefined rules(maybe unconsciously in his mind) to solving his problem, finding his missing receipt.