[tex]equals\ 7\to=7\\sum\ of\ a\ number\ and\ 9\to n+9\ (n-the\ number)\\twice\ the\ sum\ ...\to2(n+9)\\\\Answer:\boxed{2(n+9)=7}\\\\solution:\\\\2(n+9)=7\ \ \ \ |divide\ both\ sides\ by\ 2\\n+9=3.5\ \ \ \ |subtract\ 9\ from\ both\ sides\\\boxed{n=-5.5}[/tex]