i got answer as A ie 3 pounds

dont know if i am doing it the right way...but here goes my method

cont A =10

cont B= 10 ( 8 pound water 2 pound salt )

no after transfer cont B contains 15 pounds solution ( 86.67% water and 13.33% salt )

now when you transfer y pounds in cont A again, the water : salt proportion in every pound of solution in B is going to remain the same. ie 86.67 % and 13.33%

Thus y pounds will contain 13.33% salt

now after transfer cont A has 5% salt

thus we can form salt equation as 0.05( 5+y)=0.133y

solving this you get y=3.125.. but since 0.133 is recurring decimal the value of y will tend towards 3.

If i am wrong i am missing something.
:roll:

A is left with 5, B now has 15, 2/15 is the salt solution in B.

Now, as you put B into A, you are going to have an equation of,

((2/15)y)/(y+5)=.05

1.25y=3.75
y=3