Add punctuation: But even this plan failed the thing went through the ceiling as quietly as possible as if it were quite used to it
A: But even this plan failed: the 'thing' went through the ceiling as quietly as possible, as if it were quite used to it.

Add punctuation: Since DBI this means we would have IXDC but IX is the same as X so we have the solution to the equations as XDC
A: Since DB=I this means we would have IX=DC, but IX is the same as X so we have the solution to the equations as X=DC.

Add punctuation: Old Egyptians and Greeks already used weights to keep in shape
A:
Old Egyptians and Greeks already used weights to keep in shape.