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@Katharine: I only had one combo that worked. Once you wrap your head around the 19th and 20th, things should sort themselves out.

For 19th and 20th, yeah they warped my brain for a while too. The way I thought about it was this: if the 19th is true, can the 20th be true or false or is it a broken? (Remembering how "and" statements work with true/false: both have to be true for the full statement to be true.) And if the 19th is false, can the 20th be true or false or is it broken?
Seth Cohen
on /blog/120
               

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