Pythagoras' theorem

Since XY is a diagonal line, let's solve using the Pythagorean theorem of formula c² = a² + b², as we are going to graph a right-angled triangle.

Coordinate input = (x,y)

X to Y

2 - (-8) = 10 steps to the right

7 - (-3) = 10 steps up

If a = 10, and b = 10, then c = XY.

We will approach c, or XY by doing:

c²=a²+b²

c²=10²+10²

c²=200

c=√200

c=√100 √2

c=10√2

c=14.142 units, rounded to 3 decimal places.

That is a good answer mWizzard but it is not polite to add 'spoilers' such as your one.

There is no benefit to you getting people off side.