First rewrite the inequality in y = form.
3x + y > 7
Subtract 3x from both sides.
y > -3x + 7
Both graphs have a -3 slope and y intersect at 7. The only difference in the shading. Choose a test point to see if it makes the inequality true. The easiest point to choose is (0,0) if our line doesn't pass through that point.
0 > -3(0) + 7
0 > 7 is false so we want the graph where (0,0) is NOT shaded. That is the one on the left.