The distance of P(3, 4) from the x-axis is
The distance of any point from x-axis can be determined the modulus or absolute value of the y-coordinate of that point and in a similar manner, the distance of any point from y-axis can be determined the modulus or absolute value of the x-coordinate of that point
The modulus of y-coordinate is taken because distance cannot be negative.
In this case, the y-coordinate is 4 and hence the distance of the point from x-axis is 4 units.