Frequent error with "used to" in lessons using costumar
Duolingo repeatedly marks my sentences wrong when I use "used to" as opposed to "use to" for costumar. This is wrong. The correct form in English is "used to". It's a bit frustrating to have to type faulty English to get something right. http://www.grammar.cl/rules/used-to-use-to.htm
Report it! Some people do these lessons to learn English, so it's worth getting the English grammar right. You can use the Report button on the bottom of the Lesson pages whenever you see a mistake in English or Portuguese.
Although--and I'm sure you already know this--there are certain cases where "use to" is correct. http://oald8.oxfordlearnersdictionaries.com/dictionary/used-to