Question 722498
John alone for 2 days:  {{{(1/6)*2}}} amount of jobs

John plus Tom for d days: {{{(1/6+1/9)*d}}} amount of jobs


The sum of those two "amount of jobs" must be 1 when the job is done.
{{{(1/6)*2+(1/6+1/9)*d=1}}}
Solve for d.
The total time is {{{2+d}}}.