1. Systems of 3 Equations with 3 Variables

2. How to solve: Steps: Take 2 equations and eliminate a variable
Take two different equations and eliminate the SAME variable
Take the 2 new 2 variable equations and eliminate one of those variables
Plug the value into either 2 variable eq. for the value of the 2nd variable
Plug both values into original eq. to find value of 3rd variable

3. Example

4. Another Example

5. One more

6. Mrs. Thrifty-Saver invested $50,000 in three different accounts
Mrs. Thrifty-Saver invested $50,000 in three different accounts. She invested three times as much money in an account that paid 8% interest as in an account that paid 10% interest. The third account earned 12% interest. If she earned a total of $5160 in interest in a year, how much did she invest in each account?

7. Bozo goes to the amusement park to ride roller coasters, bumper cars, and water slides. The wait for the roller coasters is 1 hour, the wait for the bumper cars is 20 minutes long, and the wait for the water slides is only 15 minutes long. Bozo rode 10 total rides during his visit. Because he enjoys roller coasters the most, the number of times he rode the roller coasters was the sum of the times he rode the other two rides. If Nick waited in line for a total of 6 hours and 20 minutes, how many of each ride did he go on?

8. Seats closest to an amphitheater stage in Section A cost $30
Seats closest to an amphitheater stage in Section A cost $30. The seats in the next section, Section B cost $25, and lawn seats are $20. There are twice as many seats in section B as in section A. When all 19,200 seats are sold, the amphitheater makes $456,000. How many seats are in each section?