短语讲解：

1. He is already skilled at calculus – high-level math that often deals with rates of change.

deal with 应付; 对待; 惠顾; 与…交易
例句：Imperical edicts could deal with very varied matters.
皇帝的诏节涉及各个方面的事物。

2. The boy taught himself English in about six months by living in Singapore.

live in 住在学习[工作]的地方; 住在（某地）; 存在于…
例句：We used to live in Shanghai but now we live in Beijing.
我们以前住在上海，但现在住在北京。