how to finding out a remaining value in a query : I currently have a databases exam and one of the questions is asking me to find out how many tickets are remaining at a event. There are 5 events i think and a NumOfAdultsTickets field and a NumOfChildTickets field so i would need to add both them values together and then take away that value from 80 which is the total amount of tickets for that event location. In a query I've tried grouping the num of adults and the num of childs and then having a calculation field that adds them two values and then subtracts that value from 80 but that gives me a value of something like -1000. Please Help would be greatlly appreciated