It's given that on a graph, x is the horizontal axis and y is the vertical axis.
For point (4, 7), x = 4 and y = 7 (these are the vertical & horizontal lines). We know this because the y coordinate will always be the horizontal line and the x coordinate will always be the vertical line.
For point (3, -2), it's the same situation. Since 3 is your x coordinate, the vertical line will be x = 3. Since -2 is the y coordinate, the horizontal line will be y = -2.