Question 1006218
RT=J uniform rates for doing a job.  The job is building wall of specified height.

Each mason has a rate r and n masons have a rate nr.


Let n still be a variable for how many masons, unknown number of masons.
{{{system(14r*12=12,nr*7=120)}}}


Solve the system for r and n.
{{{14r=1}}}
{{{r=1/14}}}
-
{{{nr*7=120}}}
{{{n=120/(r*7)}}}
{{{n=120/(7(1/14))}}}
{{{n=120/(1/2)}}}
{{{highlight(n=240)}}}