。
She teaches reading and writing.
Literal
She [topic-は] reading-and-writing [object-を] is-teaching.
読み書き is a fixed compound: 読む's stem 読み ('reading') + 書く's stem 書き ('writing') = 'reading and writing, literacy.' This stem-stem compounding is productive: 飲み食い ('eating and drinking'), 行き来 ('coming and going'), 売り買い ('buying and selling').