To find the length of the line segment \( \overline{CD} \), we can utilize the information given in the problem. We have three segments:
- \( CD = x \)
- \( DE = 7 \)
- \( CE = 2x \)
We know that point \( D \) is located between points \( C \) and \( E \), so we can express \( CE \) as the sum of \( CD \) and \( DE \):
\[ CE = CD + DE \]
Substituting the expressions we have for these segments:
\[ 2x = x + 7 \]
Now we can solve for \( x \):
- Subtract \( x \) from both sides:
\[ 2x - x = 7 \] \[ x = 7 \]
Now that we have the value of \( x \), we can determine the length of \( \overline{CD} \):
\[ CD = x = 7 \]
Therefore, the numerical length of \( \overline{CD} \) is
\[ \boxed{7} \]