1. The pupil could add and subtract but hadn't learned to divide. 这名小学生能做加法和减法，但还没学会做除法。
2. They subtract this loan balance from the sale price and you get cash to buy another house. 他们从售房价格里减去这个贷款余额，然后你就可以得到现金去买另一个房子。
3. You've got to juggle the two equations, multiply that by 4, multiply that by 3, add and subtract and so on. 你必须联立这两个方程，一个乘以4，另一个乘以3，再加减等等。
4. In short, the nation's central measure of economic well-being works like a calculating machine that adds but cannot subtract. 简而言之，衡量国家经济福祉的核心指标就像一台计算器，只能增加，不能减少。
