1. 6-2 Solving Systems using Substitution
Substitution Method
Solving one equation for one variable and substituting the expression for the variable into the other equation.
How do I Solve a System of Linear Equations using substitution?
Step 1: Solve one equation for a single variable, if necessary.
Step 2: Substitute the expression for that variable into the other equation in place of that variable.
Step 3: Solve for the variable in this new equation.
Step 4: Substitute the value for the variable found in step 3 into either of the original equations to solve for the other variable.

2. 6-2 Solving Systems using Substitution
If you get an identity, like 2 = 2, when you solve a system of equations, then the system has infinitely many solutions.
If you get a false statement, like 8 = 2, then the system has no solution.