Question

Find the distance between the points given. (-10, 3) and (-10, 12) 9 15

Answer 1

The distance between the points (x₁,y₁) and (x₂,y₂):
$d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$

$(-10,3) \\ x_1=-10 \\ y_1=3 \\ \\ (-10,12) \\ x_2=-10 \\ y_2=12 \\ \\ d=\sqrt{(-10+10)^2+(12-3)^2}=\sqrt{0+9^2}=\sqrt{9^2}=9$

Another method:
The points have the same x-coordinate so they lie on the same line. y-coordinates are positive so you just subtract 3 from 12. See the picture in the attachment.

The answer is 9.

Answer 2

The way to solve it can be shorter :) 
Just look, that  these points have got the same x-coordinate, 
so they lie  on the same line, which is parallel to the OY axis, 
So  your taks is only  find different  in y-coordinate. That is
12-3 = 9 
And this is answer :)