Question 306370
Let that number be N.
{{{3N-18=N}}}
{{{3N-N-18=N-N}}}
{{{2N-18=0}}}
{{{2N-18+18=0+18}}}
{{{2N=18}}}
{{{2N/2=18/2}}}
{{{N=9}}}
Your number is 9.