Answer:
If you have a false statement at the end.
Step-by-step explanation:
When using substitution to solve a system of equations, you can tell when the system has no solution if the equation at the end produces a false statement.
For example, at the end if you have something like 3x + 1 = 3x - 4. You would subtract 3x from both sides of the equation and be left with 1 = -4.
This is a false statement, 1 does NOT equal -4. Therefore, system of equations has no solution.