George does 3/5 of a piece of work in 9 days. He then calls paul and they finish the work in 4 days. How long would paul take to do the work by himself? 1. 28 2. 35 3. 30 4. 32

Consider the expression provided 
george 1 day work=1/15
let pau 1 day work be 1/x
work to be done=1-3/5=2/5
then,a/c
4(1/15+1/x)=2/5
=>x=30
i.e:- 3)30

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3.30 days 
gorge: does 3/5 th in 9 days 
in 1 day he can do 1/15 
so in 4 days he can do =4/15
:. total work done by gorge =3/5+4/15=13/15

work left= 1-13/15=2/15

which is done by paul in 4 days so paul can do 2/15*4 in 1 day=1/30 
:. paul will take 30 days to do the job himself