 Okay, so the most general linear transformation is XB is some constant C times XA plus some constant D times TA. So it depends on just XA and TA. So no nonlinear terms like XA squared or XA times TA or TA cubed. And similar for TB. This is also the only transformation where when XA equals TA equals zero, XB and TB are also zero. So you might be asking, where is V, the velocity? Well, that's in there somewhere. C, D, E and F are constants. So maybe D is equal to V or D has a V in it somewhere. Now since Y transforms in such a boring manner in that it doesn't affect how X and T transform, we'll ignore it for now and focus just on the X and T axes. So let's say two events happen in Alice's frame. One happens at X1A, T1A and the second happens at X2A, T2A. Now we'll call delta XA and delta TA the intervals between these events. In this case, what is delta XB? How does that transform? So as a hint, work out what X1B is and X2B is and then delta XB is X2B minus X1B.