Question 1006654
Slow Machine:  {{{1/x}}} JOBS per HOUR

Fast Machine  {{{3/x}}} jobs per hour

Both Machines Combined:  {{{1/x+3/x=1/3}}} jobs per hour




{{{(1+3)/x=1/3}}}


{{{4/x=1/3}}}


{{{highlight(x=12)}}}


Slow machine does one job alone in 12 hours.
Fast machine does the job in 4 hours.