Which one of the following is not a step of problem-solving approach?

Observation is not a specific step of the problem-solving approach. The problem-solving approach typically involves: (1) identifying/visualizing the problem situation, (2) formulating a hypothesis or plan, (3) attempting to solve through trial and analysis, and (4) drawing conclusions from the results. While observation is part of scientific inquiry generally, it is not listed as a discrete step of the structured problem-solving method.