Question 912783
(Adjusted mistake on Oct. 14, 2014):


Let T be the time for Mr. Twain to do the job alone.


Their rates:
Mr. B, 1/9
Mr. Twain, 1/T
B & Twain Combined, 1/9+1/T


The  resting time is not important in the problem.


The whole job was split into two parts.  Mr B for 5 hours and both workers for 2 hours 20 minutes.  


{{{highlight((1/9)5+(1/9+1/T)(2&1/3)=1)}}}
Solve the equation for T.


Just to help you be more confident, this is a work or task problem with uniform rates using the basic rule RT=J rate time job.  In the example problem, the amount of job to be done is 1 job.