Answer :

[tex]x-the\ number\\\\x+24=3x\ \ \ \ \ \ |subtract\ 24\ from\ both\ sides\\\\x=3x-24\ \ \ \ \ \ \ |subtract\ 3x\ from\ both\ sides\\\\-2x=-24\ \ \ \ \ \ \ \ |divide\ both\ sides\ by\ (-2)\\\\\boxed{x=12}\leftarrow answer[/tex]