There are 28 rungs in a Ladder
He was in middle, so let assume it has point x
Then he climbs up 6 rungs, and then 10rungs down.
which is x+6, and then x+6-10=x-4.
then he reaches top by climbing 18rungs, that is x-4+18=x+14.
now, as he was in middle i.e. x and reached top i.e. x+14 means
total # of rungs= 14*2 = 28.