Question 981198
Uniform Rates, Doing  A  Job.
One job for this exercise is "build a wall".
RT=J to relate work rate, time, quantity of job or jobs.


Agents working in a team give the team a rate the sum of the rates of the individual team members.


Let r be work rate for one worker.
Let t be unknown time for the question clause.
First clause:  {{{18r*10=1}}}
Second clause: {{{10*r*t=1}}}


Understanding the discussion and how the two equations were formed must be, before you continue.


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The rest is just arithmetic, or simple algebra steps.