Final answer:
To find the number of adult tickets sold for the school play, the two equations S = A + 65 and A + S = 765 are used, which reveals that 350 adult tickets were sold.
Step-by-step explanation:
The question asks us to determine the number of adult tickets sold when a total of 765 tickets were sold for a school play, and there were 65 more student tickets sold than adult tickets. Let's call the number of adult tickets A and the number of student tickets S. We know that S = A + 65 and that the total number of tickets is A + S = 765.
Substituting the first equation into the second, we have:
A + (A + 65) = 765
2A + 65 = 765
2A = 765 - 65
2A = 700
A = 350
So, 350 adult tickets were sold.