To find the undefined value in the equation
\[ 22 = \frac{4 + 5x}{9x - 6}, \]
we need to determine when the denominator is equal to zero because division by zero is undefined.
Set the denominator to zero:
\[ 9x - 6 = 0. \]
Now, solve for \(x\):
\[ 9x = 6, \]
\[ x = \frac{6}{9} = \frac{2}{3}. \]
Thus, the undefined value for the equation is
\[ \frac{2}{3}. \]