1. Warm Up  If x = 3, y = 4, and z = 5, solve the expression.  1.) x + y + z  2.) z(x + y)  3.) y – z * x

3. Objective  Solve systems of equations using substitution.

4. Substitution Method  You can solve linear systems by solving one of the equations for one of the variables and plugging the result into the other equation.

5. Example 1 – Using Substitution  What is the solution of the system? Use substitution. y = 5x x + y = 12

6. Example 2 – Solving for a Variable and Using Subst.  What is the solution of the system? Use substitution. 7x – 3y = 2 -2y + x = -6

7. Example 3 – Using Systems of Equations  The school bookstore sells T-shirts for $8 and sweatshirts for $12. Last month, the bookstore sold a combined 37 T-shirts and sweatshirts for a total of $376. How many T- shirts were sold?

8. Warm Up  Solve the system using substitution.  1.) y = 4x 4x + y = 16  2.) 7x – 2y = 1 2y = x - 1

9. Example 4 – Systems with Infinitely Many Solutions or No Solutions  How many solutions does each system have?  A.) x = -3y + 4  6y + 2x = 8  B.) y = 4x – 9  y – 4x = 6

10. Assignment  Pg. 371 – 372 (11 – 19 all, 23, 26 – 28 all)