addition and subtraction

例句：

1. 1. The teacher added anew lesson to the class schedule.
   老师在课程表上增加了一个新课。
2. 2. The companyadded a new product line to its portfolio.
   公司在其投资组合中增加了一个新产品线。
3. 3. Theamount of money added to the account increasedby $500.
   账户中的金额增加了500美元。