Simplify the following expression. \( 11 x^{2}-5+13 x-9 x^{2}-15 \)

To simplify the expression \( 11 x^{2}-5+13 x-9 x^{2}-15 \), combine like terms. First, group the \(x^2\) terms: \(11 x^{2} - 9 x^{2} = 2 x^{2}\). Next, combine the \(x\) terms, which gives: \(13 x\) (no other \(x\) term to combine with). Lastly, combine the constant terms: \(-5 - 15 = -20\). Putting it all together, the simplified expression is: \(2 x^{2} + 13 x - 20\).