Alright, so it would be helpful to think about this question in terms of units. You're given a distance (meters) and speed (meters per second). You're asked for time (which is in seconds).
If you do [tex] \frac{meters}{meters/second} [/tex], your answer will be in seconds. So divide your distance (2.28 x 10^11 meters) by your speed (3.00 x 10^8 meters/second), and you should get your time!
