The original hexagon's side length was 5.
The corresponding side length to the new hexagon is 6.25,
to find the scale factor, we need to find out what times 5 got to 6.25
We can write this out as:
5x = 6.25
Divide 5 on both sides:
x = 1.25
The scale factor is 1.25 :)
Remember that the scale factor represents what the side length is being multiplied by to get the new length :D