っで　at beggining of sentence.

I said to a person that i`m going to Tokyo:
東京へ行きます。


the person said:
東京へ行く。
っで合ってますか。

*I think it's で without っ.

「東京へ行く」で合っていますか。= Is is correct「東京へ行く」?

The literal translation of this DE might be "with (saying)" though it's not correct in English. 

We also have って, for example, 「東京へ行く」って言いました and it means "that" of "(Someone) said THAT she/he would go to Tokyo". 

I hope this helps you.