This topic primarily focuses on identifying line equations with slopes that are perpendicular to given line equations. It involves using the property that the slopes of two perpendicular lines are negative reciprocals of each other. Each problem presents an original line equation in slope-intercept form, \( y = mx + c \), and asks to select from multiple choices the equation of a line with a perpendicular slope. Overall, the skill practiced is understanding and applying the concept of slope, particularly how it relates to perpendicularity in the context of linear equations.