What is the undefined value for 22=4+5x/9x−6

To find the undefined value in the equation

\[
22 = \frac{4 + 5x}{9x - 6},
\]

we need to determine when the expression on the right side becomes undefined. A fraction becomes undefined when the denominator is equal to zero. Thus, we focus on the denominator \( 9x - 6 \) and set it equal to zero:

\[
9x - 6 = 0.
\]

Now, solve for \( x \):

\[
9x = 6,
\]
\[
x = \frac{6}{9} = \frac{2}{3}.
\]

Therefore, the value that makes the expression undefined is

\[
\boxed{\frac{2}{3}}.
\]