How are SN1 reactions written?
Since the rate-determining step is the loss of a leaving group, we want excellent leaving groups. Moreover, since
Afterward, the intermediate with the positively charged oxygen is too high in energy to be very stable, so methanol will deprotonate it to the give the molecule I made at the end.
These take a lot of practice, and this is normally where organic chemistry gets hard for students (and where I see lots of drops and quiz/exam fails, unfortunately). Get it together or surrender is what I say. :)