15 of what number is 12? EXPLAIN

According to the law of supply,suppliers want to sell their product at prices

In a study, people were asked to imagine simple occasions that made them happy and to remember events that made them feel proud about themselves. it was observed that the subjects developed an increasingly positive attitude. these changes are known to be healthy, leading to greater physical activity and reducing unhealthy habits. based on this excerpt, we can conclude that a positive attitude .

Advances in technology generally result a.) a higher standard of living for everyone b.) greater productivity c.) more jobs for everyone d.) more government regulation