Tables in Twenty Twelve – inconsistent widths on pages

I’ve got two different forms in tables on different pages. Both have labels on the left and input areas on the right.

On one page, the two columns are 50%-ish in size.

On another page, the label columns are 15% and the input ares are 85%.

I’d like these to be balances with about 30-70 ratio. But how would I set these to be those values since they’re all in <td> areas? The columns don’t have unique selector ids.

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