1. **State the problem:** We need to find the value of $v$ in parallelogram CDEF where side $CD = 2v$ and the opposite side $EF = v + 19$. 2. **Recall the property of parallelograms:** Opposite sides of a parallelogram are equal in length. 3. **Set up the equation:** Since $CD$ and $EF$ are opposite sides, we have: $$2v = v + 19$$ 4. **Solve for $v$:** Subtract $v$ from both sides: $$2v - \cancel{v} = \cancel{v} + 19 - v$$ $$v = 19$$ 5. **Conclusion:** The value of $v$ is 19.