Tickets at a play cost $10 or $14. if 800 tickets were sold and $9,040 was collected by the box office, how many $14 tickets were sold?

STEP 1:
determine equations needed

x= # of $10 tickets
y= # of $14 tickets

QUANTITY EQUATION
x + y= 800

COST EQUATION
$10x + $14y= $9,040

STEP 2:
multiply quantity equation by -14

-14(x + y)= -14(800)
-14x - 14y= -11,200

STEP 3:
add new quantity equation in step 2 to cost equation of step 1 to solve for x using elimination

-14x - 14y= -11,200
10x + 14y= 9040
y term cancels out

-4x= -2160
divide both sides by -4

x= 540 ten dollar tickets

STEP 4:
substitute x value in step 3 into either original equation

x + y= 800
540 + y= 800
subtract 540 from both sides

y= 260 fourteen dollar tickets

ANSWER: There were 540 $10 tickets and 260 $14 tickets sold.

Hope this helps! :)