Problem :
men(x1) or women(y1)
can complete a work in
days(z1). men(x2) and
women(y2) started doing the
work. After days(z2),
men(x3) and
women(y3) left the work.

The Rest shall finish the work in how
many days ? Answer -
days(z3)

Total no. of days to complete the work ?
Answer-
days(z2+z3)

Formula-( z1-z2*A1)/(A1-A2) where A1=(x2/x1) + (y2/y1) and A2=
(x3/x1) + (y3/y1)