-3cu+9xy-18xy

To simplify the expression \(-3cu + 9xy - 18xy\), we can combine like terms.

First, let's focus on the terms with \(xy\):

\[ 9xy - 18xy = -9xy \]

Now, we can rewrite the entire expression:

\[ -3cu - 9xy \]

So, the simplified expression is:

\[ -3cu - 9xy \]