Question 964654
The rate of agents working at the same time is the sum of their rates.


Let t be the time for B and C to finish the job, AFTER A and B worked for one hour.
{{{(1/4+1/6)*1+(1/6+1/8)t=1}}}
This is two expressions of job portions, summed.  One for 1 hour by A and B, the other for unknown time by B and C.


Solve for t.