

この図に線をもう一本加えると、三角形になります。
スープに塩を少し加えてください。
この図形に何を加えれば正方形になりますか。
"くわえる(加える)" is in the lesson "Geometric figures" (Level 45), along with 11 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.