The 100% of tickets are 320 tickets (this is Haley's goal), she made 112 tickets. To determine what percentage of 320 does 112 represent you can use cross multiplication:
320 ____ 100%
112 _____ x%
Both relations are at the same ratio so that
112 tickets represent 35% of 320, which means that she made 35% of the admission tickets so far.