Question 713486
The rates of Marcus and Tony combine by addition when they work together.  "Lay a slab of concrete" is 1 job. Treat the rates as the number of jobs per hour.


Marcus' rate is {{{1/8}}} jobs per hour.
Tony's rate is {{{1/2}}} jobs per hour.
Tony and Marcus at the same time, {{{(1/8+1/2)}}} jobs per hour.  Call this rate, R.


The price for the 1 job is $45.00/hour.  


Jobs*(1/jobsPerHour)*(dollarsPerHour)= dollars.   
That would be units of
jobs*(hours/job)*(dollars/hours)=dollars.  That would be how the units work.


Here would be how the numbers would work:
{{{1*(1/R)*45}}}, the labor cost estimate.