Well, first we have to figure out how many tickets are already sold. To do this you have to first make 1/5 and 2/3 have the same denominator. You can do this by multiplying 1/5 by 3 to get 3/15, and 2/3 by 5 to get 10/15. 3/15+10/15=13/15, so 2/15 of the tickets are 300 tickets, so 1/15 of the tickets is 150 tickets. 150*15 is 2250 so there are a total of 2,250 tickets for the match.
Hope this helps!