How long are the line segments between points

a) [[$ (3, 6) $]] and [[$(9, 6)$]]
Length of the line segment:

b) [[$(-3, 2)$]] and [[$(2, 2)$]]
Length of the line segment:

c) [[$(1, 4)$]] and [[$(1, 8)$]]
Length of the line segment:

d) [[$(-2, -3)$]] and [[$(-2, 5)$]]
Length of the line segment: