</span></span></span>Combine Like Terms:<span>=<span><span><span><span>18x</span>+<span>−9</span></span>+<span>−<span>9x</span></span></span>+<span>−18</span></span></span><span>=<span><span>(<span><span>18x</span>+<span>−<span>9x</span></span></span>)</span>+<span>(<span><span>−9</span>+<span>−18</span></span>)</span></span></span><span>=<span><span>9x</span>+<span>−<span>27