Answer: 2
Solution:
Initial Coordinates=(5,0)=(xi,yi)→xi=5, yi=0
Final Coordinates=(10,0)=(xf,yf)→xf=10, yf=0
Scale factor=xf/xi=yf/yi
We divide the final coordinates by the initial coordinates. In this case the ordinates (yf and yi) are zero and we can't divide by zero, but the abscissas (xf and xi) are different of zero, then we can use them:
Scale factor=xf/xi=10/5
Scale factor=2