To solve the system of equations using the substitution method, we have the two equations:
- \( y = -3 \)
- \( y = 2x + 1 \)
Since the first equation gives us a direct value for \( y \), we can substitute that value into the second equation.
Substituting \( y = -3 \) into the second equation:
\[ -3 = 2x + 1 \]
Next, we solve for \( x \):
- Subtract 1 from both sides:
\[ -3 - 1 = 2x \] \[ -4 = 2x \]
- Divide both sides by 2:
\[ x = -2 \]
Now we have the solution for \( x \). To find the value of \( y \), we can substitute \( x = -2 \) back into the first equation (though we already know what \( y \) is):
\[ y = -3 \]
Thus, the solution to the system of equations is:
\[ (x, y) = (-2, -3) \]
So the final answer is:
\[ \boxed{(-2, -3)} \]