1. Warm Up Solve for 3x + 2(x – 1), when x = 3
Solve the linear system by graph and check method.
3x + y = 5
2x – y = 10

2. 7.2 Solving Linear Systems by Substitution
Algebra 1
7.2 Solving Linear Systems by Substitution

3. Substitution Method
3x + y = 5 2x – y = 10

4. Substitution Method
x = 2y 2x + 6y = 15

5. Which variable do we solve for?
3x – y = -9
2x + 4y = 8
x + 3y = -11
2x – 5y = 33
x – 3y = 0
y – 2x = 10

6. Which variable do we solve for?
When using substitution, you will get the same solution whether you solve for y first or x first. You should begin by solving for the variable that is easier to isolate (usually the variable that has a coefficient of 1).

7. Use substitution to solve the linear system.
Practice Examples
Use substitution to solve the linear system.
2x + y = 4
-x + y = 1
3x – y = 0
5y = 15

8. Write and Use a Linear System
In one day a movie theater collected $4275 from 675 people. The price of admission is $7 for an adult and $5 for a child. How many adults and how many children were admitted to the movie theater that day?