To solve the equation \( 6 - 4f + 9 = 13 - 4f \), we start by simplifying both sides.
Combine like terms on the left side:
\[ 6 + 9 = 15 \]
So, the equation simplifies to:
\[ 15 - 4f = 13 - 4f \]
Next, we can add \( 4f \) to both sides to eliminate \( -4f \) from both sides:
\[ 15 = 13 \]
This statement is not true; \( 15 \) does not equal \( 13 \).
The conclusion here is that the equation has no solution. The original equation is inconsistent.