The distance between any two points (x1 , y1) and (x2 , y2) is given as sqrt ((x1 - x2)^2 + (y1 - y2)^2)
Here the points are ( 2x+3, 8) and (2x, 4)
The distance between the two is
sqrt [(2x + 3 - 2x)^2 + (8 - 4)^2]
=> sqrt [3^2 + 4^2]
=> sqrt( 9 + 16)
=> sqrt 25
=> 5
The distance between the points is 5