If the preimage point is (5,0) and the image point is (10,0)
then the scale factor is k = 2
Basically the coordinates of the old point have doubled (multiplied by 2)
x = 5 is the old x coordinate
x = 10 is the new x coordinate (5*2 = 10)
y = 0 is the old y coordinate
y = 0 is the new y coordinate (0*2 = 0, no change)