The boundary line is x = 3 which is a vertical line through the two points (3,0) and (3,1). The x coordinate must be 3. The y coordinate can be any real number you want.
The boundary line is a dashed line since "or equal to" is missing in the inequality sign. Points on the dashed boundary line are NOT part of the shaded solution set.
Shade to the left of the dashed boundary to represent all (x,y) points where x < 3. For example, the point (0,5) is a solution since x = 0 makes x < 3 true. This point is in the shaded region.
See the diagram below