Question 1155236
at the valve factory w workers made v valves in 5 days
5w man-days to make v valves
 how many days would it take n more workers to make the same number of valves?
v = v
let d = no. of days required  with n more workers
therefore
d(w+n) = 5w
d = {{{(5w)/((w+n))}}}, days