Question 1199446
N, how many workers
R, work rate for 1 worker
T, time of working
W, amount of work

{{{highlight_green((NR)T=W)}}}----basic rule



let r be the work rate of any one man, and x be the time asked for.
{{{system(20r*8=36,25r*x=54)}}}



If you divide the second equation by the first equation,..........

{{{(25x)/(20*8)=54/36}}}

{{{(5/4)(1/8)x=(9/9)(6/4)}}}

{{{(5/4)(1/8)x=3/2}}}

{{{x=(3/2)(8)(4/5)}}}

{{{x=3*4*4(1/5)}}}

{{{highlight(x=9&3/5)}}}