D5000 35mm f1.8 with extension tubes

Hi, I need some advice.

i have bought a 35mm f1.8 prime lens and love it.  I am currently borrowing a friends kenko extension tubes, but can't get any shots at a decent working distance.

what would you expect the working distance to be? I am practically on top of the subject which isn't good.

please help .

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Im new to photography - any help is always welcome.