Question 961502
Mudog's rate of working is:
{{{ 8/3 }}} jobs / days
Jimmy's rate of working is:
{{{ 5/2 }}} jobs/days 
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Let {{{ x }}} = the number of jobs 
Mudog gets done in {{{ 3 }}} days
{{{ x = ( 8/3 )*3 }}}
{{{ x = 8 }}} 
There are {{{ 31 }}} jobs left to do
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With both working together:
{{{ 8/3 + 5/2 = 31/t }}}
Multiply both sides by {{{ 6t }}}
{{{ 16t + 15t = 186 }}}
{{{ 31t = 186 }}}
{{{ t = 6 }}}
They would have to work together for
6 more days to complete all the 39 jobs