7.2 Solving Systems by

Substitution Warm Up and Discuss with your Partner 1) Solve the system of Equations by Graphing: 2) Solve the system of Equations by Graphing:

2y x 7

3x 4y 8

2x 3y 9

y x 7

Think and Discuss: Did you experience any frustrations with the problems above? Describe in a couple sentences below:

Alternatives to Graphing: SUBSTITUTION METHOD! Think and Discuss: What does the word SUBSTITUTE mean?

Solve the following using the Substitution Method.

y x 7

x 4y 8

2x 3y 9

y x 7

7.2 Notes

Steps for SUBSTITUTION METHOD!

1. Decide which variable is easiest to _____________________________.

2. ____________________________ for that variable.

3. ____________________________ the expression from step 2 back into the OTHER equation.

4. Use the found value of one variable to find the value of the other variable.

5. _______________________ both values by plugging them back into the original equation.

Let’s Practice Substitution

Ex. 1

x 2y 7

x y 23

Ex. 2

7x 2y 24

4x y 8

Ex. 3

y 2x 19

y x 7

Ex. 4

y 2x

y 3x 2

Ex. 6 Gina went shopping for holiday presents. She bought boxes of chocolates and boxes of ornaments for her coworkers. Boxes of chocolate cost $8 each and boxes of ornaments cost $6 each. She buys a total of 22 boxes and spends $152. How many boxes of chocolates and how many boxes of ornaments does she buy?