Using the nested tables approach is a bit more complex than my suggestion.

The first column doesn't want to resize because the other columns also contain words (no spaces) that are the full width of the column and Word is trying to satisfy all the column widths so words don't break. There is a Table Properties setting that says "automatically resize to fit contents" and this is greyed out (probably because the table is nested.

The easiest fix for the table "Mathematics" column is to allow the text in the cell to get closer to the left and right borders. You do this by selecting the inner table and right clicking it and choosing Table Properties > Table > Options. Set the Default Cell Margins on the left and right to 0.1cm (it was 0.19cm). This will solve your Mathematics issue and reduce the line count a little bit.

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Andrew Lockton
Chrysalis Design, Melbourne Australia