

じゅうに時に昼ご飯を食べます。
じゅうに月はクリスマスがあります。
弟はじゅうに歳ですか?
"じゅうに(十二)" is in the lesson "Numbers" (Level 3), along with 19 other useful words. LinDuo has 180 topic lessons like this one, 2,379 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.