Question 773494
r, the work rate of 1 man

For 5 men working 10 days to do 1 "piece of work"
{{{5r*10=1}}}

or

{{{r=1/50}}}


Five men worked for 4 days and then 2 men worked for some x days to finish.
{{{highlight_green(5(1/50)*4+2(1/50)x=1)}}}

{{{5*4+2x=50}}}

{{{2x=50-20}}}

{{{2x=30}}}

{{{highlight(x=15)}}}