Answer:
7
Explanation:
The distance is given by the length of a line perpendicular to x=4, that contains point (-3,4). Since x=4 is vertical, the perpendicular line is horizontal, so it must be y=4 to pass through (-3,4). y=4 crosses x=4 at (4,4).
The distance from (-3,4) to (4,4) is 4 - -3 = 7.