Final answer:
Kyle and Matthew's supportive relationship in their businesses is best described by social exchange theory, which focuses on the mutual benefits that incentivize the continuation of their association.
Step-by-step explanation:
The relationship between Kyle and Matthew, who support one another's businesses, can best be described by social exchange theory. This theory posits that people form and maintain relationships by weighing the costs and benefits. In a business context, this means that the associates would continue supporting each other's businesses as long as they perceive the benefits of doing so to outweigh the costs. This mutual support is indicative of a strategic, benefit-focused approach that is aligned with the principles of social exchange theory.