Ms. Thomas took her family and friend to the movies. There were a total of 16 people. Children tickets cost $6 and adult tickets cost $9. She spent a total of $129. How many adults went to the movies?

11 adults

Step-by-step explanation:

First, set up a system of equations:

Let x = number of children and y = number of adults

There is a total of 16 people, so x+y = 16. This is your first equation.

Each child ticket costs $6, so 6x = cost of children's tickets based on the number of children present (x)

Each adult ticket costs $9, so 9y = cost of adult's tickets based on the number of adults present (y)

The total cost of tickets is $129, so 6x+9y = 129. This is your second equation.

Your system of equations is now this:

x + y = 16

6x + 9y = 129

You can solve this system using the method of elimination, where we will eliminate the variable x (number of children), since we are focused on y (number of adults).

Multiply the top equation by - 6. This will give the following equation:

-6x - 6y = - 96

You can now solve the system of equations by placing the new equation under the second equation like this:

6x + 9y = 129

-6x - 6y = - 96

Now, add the two equations together.

6x + (-6x) = 0

9y + (-6y) = 3y

129 + (-96) = 33

After doing this, you get the following equation:

3y = 33

As you can see, the variable x has been eliminated, and you are left with y.

Solve the equation for y:

3y = 33

y = 33/3 = 11

y = 11 adults