Answer:
45 cause any value inside mod function always return to postive
Let x tickets sold be adults, then (1024-x) were of childrens tickets, 9x+(1024-x)4 = 7680. The above equation is for total money solve it you will get x=720 hence, number of adult tickets were 720 and number of child tickets were 300 :)
I don't understand it sorry
