i thought that at first, but then realised that thats what it means in the ifrst instance - if all 4 had lied, then because two of them said the same thing, there are 3 answers provided that are incorrect. that leaves 4 possible actual days of the week - the ones that none of the aboriginals said it was
this is what you were saying - the days they dont mention
you got the first bit right, the width after three wishes is 1/3cm, but then you said the area was 16cm. its meant to be 4cm^2, which is not the same as 16cm
so instead of 1/3 * L = 16cm, it should be
1/3 * L = 4 to find length after 3 wishes
i havent checked my answer, but looking at your post, that jumped out at me.
hope it helps