Answer:
8.6
Explanation:
There is an easier way which is finding the slope of the equation but I'm going to stick to distance formula(which is easier for me).
For this, you would have to know the distance formula which is 
d=√(x2−x1)^2+(y2−y1)^2
Which simplifies into 
 which you get from 6-(-1) and -2-(-7)
 which you get from 6-(-1) and -2-(-7)
Further simplifies into 

=

=8.602325