Answer:
350 adult tickets were sold
Step-by-step explanation:
Let "a" represent the number of adult tickets sold. Then the number of student tickets is (a+69) and the total number of tickets sold is ...
a + (a+69) = 769
2a = 700 . . . . . . . . subtract 69
a = 350 . . . . . . . . . divide by 2
350 adult tickets were sold.