The X2 cannot be on any of the numbers marked with a red line. The blue arrow learns us it has to be at 16,40,55 or 74. Thus, X2 has to be at the only remaining possible position: The tile with number 16.
Be aware : Unlike many other games the X2 doubles what you won until the moment you collect the X2. In most other games it doubles all what you will win after collecting the X2.