To solve the equation \( 5^{2x - 1} = 125 \), we first express \( 125 \) as a power of \( 5 \).
We know that:
\[ 125 = 5^3 \]
Now we can rewrite the equation:
\[ 5^{2x - 1} = 5^3 \]
Since the bases are the same, we can set the exponents equal to each other:
\[ 2x - 1 = 3 \]
Now, solve for \( x \):
- Add \( 1 \) to both sides:
\[ 2x = 3 + 1 \] \[ 2x = 4 \]
- Divide both sides by \( 2 \):
\[ x = \frac{4}{2} \] \[ x = 2 \]
Thus, the solution is:
\[ \boxed{2} \]