Home/Eighth Grade Math/Week 23: Systems of equations/Lesson 6

Solve a System of Equations Using Substitution

Substitution replaces one variable with an equivalent expression.

Lesson 6

Concept

Steps: 1. Solve one equation for one variable. 2. Substitute into the other equation. 3. Solve for the remaining variable. 4. Back-substitute to find the other variable. Example: y = x + 2 2x + y = 11 Substitute: 2x + (x + 2) = 11 3x + 2 = 11 3x = 9 -> x = 3 y = 3 + 2 = 5 Solution: (3,5)

Try it

Practice: Solve a System of Equations Using Substitution.