The answer is 110 adult tickets. Let x= student tickets and y= adult tickets.
We know that the total tickets sold was 440. That means the total number of student tickets (x) plus the total number of adult tickets (y) equaled 440. Putting it into an equation, you get:
x+y=440
Now we know that the amount of student tickets is equal to three times as many adult tickets, so in an equation that is seen as:
x=3y
In order to solve for one variable, plug in 3y for the x value of the first equation to get:
y+3y=440
then solve:
4y=440
y= 440/4
y=110
The total number of adult tickets sold was 110 tickets.
(This method used in math is technically called "Solving Systems of Equations", just fyi).