"We are Anna and Lukas."
Translation:Wir sind Anna und Lukas.
I found a helpful way in which to remember when to use seid vs. sind with the words ihr, wir, and sie (which I know a lot of people have trouble with) is that wir and sie have i as the second letter, so they go with sind becauae it has i as the second letter. Then the ither would go with the othee, so ihr would go with seid. Hopr this helps and, please, correct me if I am wrong on this.
"sie sind" = "they are", "ihr seid" = "you are" (several persons informal)
Always look at the "tips and notes". https://www.duolingo.com/skill/de/Basics-2/tips-and-notes