so, if the legs are a and b and the hypothuse is c then
a²+b²=c²
the distance bewteen the points is the hyptohuse
the legs are the distances between th x and y values
so
(7,11) and (-1,5)
distances between the x values are 1 leg
that is from 7 and -1, a distance of 8 units
distances betweeen the y values are the other leg
that is from 11 to 5
that is 6 units
a²+b²=c²
8²+6²=c²
64+36=c²
100=c²
sqrt both sides
10=c
the distance between them is 10 units