Calculate the distance between A(7, 3) and B on the x-axis whose abscissa is 11.

The coordinate of point B on the x-axis whose abscissa is 11, are (11, 0).

Distance between 2 points (x₁, y₁) and (x₂, y₂) = $\sqrt{(x$2 - x1)^2 + (y2 - y1)^2}

Distance between A(7, 3) and B(11, 0) =

$= \sqrt{(11 - 7)^2 + (0 - 3)^2}\\[1em] = \sqrt{4^2 + (-3)^2}\\[1em] = \sqrt{16 + 9}\\[1em] = \sqrt{25}\\[1em] = 5$

Hence, the distance between A(7, 3) and B on the x-axis, whose abscissa is 11, is 5 units.