The expression "3x + 2" is a linear equation in one variable, where x represents an unknown value. The coefficient "3" indicates that x is multiplied by 3, while the constant "2" is added to the result. This type of equation can be used to model various real-world situations, such as calculating total costs or distances. In a graph, "3x + 2" represents a straight line. The slope of the line is 3, meaning for every increase of 1 in x, the value of the expression increases by 3. The y-intercept is 2, which is the point where the line crosses the y-axis when x is zero.