Hi Nick,
The basic equation is distance equals rate times time.
The time (t +2) for the first plane is 2 hours more than the 2nd plane's time (t) when they meet.
The rates are 180 for the first plane and 900 for the second plane.
The distance that each plane has flown is the same when they meet.
So rate x time for the first plane = rate times time for the second plane.
Have fun solving this.
Dan