Seems more likely to be translated correctly as "How much is one plus two."

"How much is one plus two." = "Berapa satu tambah dua ?"

It's the same question, using another construction and word order.

I'm sure the other languages started out like this too when they were in beta, but you'd think duo would have the system figured out by now. Get an editor to work on the L1 phrases, please. Terima kasih banyak.