In each graph, take a any point on either side and substitute in the inequality. Then check if it satisfies the inequality.
For graph 1, take a point (0,0).
substituting it we get,
y>4x-2 ⇒ 0>-2. This is true yet the region where (0,0) is, is shaded. So, wrong graph.
For graph 2, take point (0,0).
y>4x-2 ⇒ 0>-2. This is true but againt the region is shaded. so, wrong graph.
For graph 3, take point (0,0)
y>4x-2 ⇒ 0>-2. This is true. Since the point (0,0) is in this region, which is not shaded, it means that this is the required region. The correct graph is graph 3.