To solve for \( b \), we will use the information given in the problem:
- \( Y \) is the midpoint of segment \( XZ \), which means that the lengths \( XY \) and \( YZ \) are equal.
- We are given two expressions for those lengths:
- \( XY = 2b - 1 \)
- \( YZ = 26 - 4b \)
Since \( Y \) is the midpoint of \( XZ \), we can set the two expressions equal to each other:
\[ XY = YZ \]
Substituting the expressions for \( XY \) and \( YZ \):
\[ 2b - 1 = 26 - 4b \]
Now, we will solve for \( b \):
- First, add \( 4b \) to both sides:
\[ 2b + 4b - 1 = 26 \]
This simplifies to:
\[ 6b - 1 = 26 \]
- Next, add \( 1 \) to both sides:
\[ 6b = 26 + 1 \]
\[ 6b = 27 \]
- Now, divide by \( 6 \):
\[ b = \frac{27}{6} \]
- Simplifying \( \frac{27}{6} \):
\[ b = \frac{9}{2} = 4.5 \]
Thus, the solution for \( b \) is:
\[ \boxed{4.5} \]