Question

find the perpendicular distance of A(10,12) from y-axis

Answer 1

10 units.
From y axis perpendicular distance is the units from x axis.So distance is 10 so 10 units.

Answer 2

The point on the y-axis is (0, 12)

Distance between (10, 12) and (0, 12)

$\bf\huged=\sqrt{(0-10)^2+(12-12)^2}$

$\bf\huge =\sqrt{100+0}$

= 10 units