Who did more work a man walking 20km up a hill in 1 hour or a man bycicling 20km up the same hill in 30 minutes

-- The amount of work each man did is exactly the amount of potential energy he had when he arrived at the top.

-- Potential energy = (mass) x (gravity) x (height)

-- You can see from the formula that the time is not involved, so we don't care which man climbed the hill faster.

-- Also from the formula, it depends on gravity, and height of the hill.  Those numbers were the same for both men, so we can ignore those parts too.  

-- The only thing left in the formula is (mass).  Whichever man lifted more mass up the hill is the one who did more work.  The question doesn't tell us anything about the mass of the men, so we really don't have enough information to answer the question.

-- IF both men have the same mass (and weight), then the man on the bicycle did more work.  (In addition to himself, he had to lift the bicycle up the hill.)