Question 347507
The setup on this one is
{{{t/M + t/J = 1}}}
where M and J are the times it would take each person alone and t is the amount of time they work together.  The 1 represents the whole job, but now that I look at your problem, that fact is missing...here's how it would go if it were a 1...
Here M = J - 6 so our equation becomes
{{{14/(J - 6) + 14/J = 1}}}
To solve this, multiply by the LCD, which is J(J - 6), and get
14J + 14(J - 6) = J(J - 6)
14J + 14J - 84 = J^2 - 6J
Consolidating, we get
J^2 - 34J - 84 = 0
and go from there...