<PRE><B>Question 598688</B>
Let time taken by Alan alone = A hrs (= 6 hrs)
time taken by Tracey alone = B hrs ( unknown )
and time taken when they work together = C hrs (= 3hrs 20min OR 10/3 hrs)

According to the formula 
{{{1/A+1/B=1/C}}}
we get
{{{1/6+1/B=3/10}}}
{{{1/B=3/10-1/6}}}
{{{1/B=4/30=2/15}}}
therefore B =15/2

So Tracey alone would take 7 hours 30 minutes to complete the job</PRE>