In one hour Lisa can do 1/7 of the job, and in one hour the new clerk can do 1/8 of the job. Working together for one hour they can do (1/7) + (1/8) of the job.
[tex]\frac{1}{7}+\frac{1}{8}=\frac{15}{56}[/tex]
Therefore when working together they will take 56/15 = 3.733 hours.
The answer is 3.733 hours or 3 hours and 44 minutes.
