1.Weren't you ______ to help me wash the dishes? (suppose)

It's PAST TENSE. You can tell from the tense of "Weren't" - so which form of "suppose" should you use?

I know this is 12 years late, but it is "supposed" since it is past tense. Just remember the "ed" for most past tense words.

No, the correct form of "suppose" in this sentence would be "supposed."

To form the sentence correctly, you would say, "Weren't you supposed to help me wash the dishes?"

The word "supposed" is the past participle form of the verb "suppose." In this context, it is used to indicate that someone was expected or required to do something.