"I thank the invitation."
Translation:Eu agradeço pelo convite.
"I thank the invitation" is a very awkward English sentence. The literal translation to Portuguese was accepted so I was happy.
The other way round won't be so easy because you could be given either their answer "Eu agradeço pelo convite" or my answer "Eu agradeço o convite" and be expected to come up with "I thank the invitation". These two sentences, as far as I can tell don't really mean the same thing, one is "I thank (you) for the invitation" and the other says "I appreciate the invitation" (I struggled a bit with what word to use here, "thank" doesn't work, so I asked Google Translate).