Question

6 men or 10 women can do a piece of work in 12days.in how many days the same work can be done by 3men and 5 women?

Answer 1

the work was already done by the 6 mn n 10 women nothing left to do

Answer 2

if we put x for a man, and y for a woman:
we have,
6*x=12
10*y=12

we now have values for both x and y, 
x=2, and y=1.2

now if you have 3 men and 5 women, then:
3*x+5*y= (3*2)+(5*1.2)=6+6=12 days

that means the work will be done in also 12 days