Differences between for and in

你問得咁簡單，只可以簡化回答：

For係「關於」/ 「由於」，
In係「在...裏」

你的例子：

In economics (在經濟學裏,,,
In the economy (在這個經濟[體系]內...
For the economy (關於經濟或由於經濟...

In this/the strategy... (在這個策略裏[中]...
For the strategy to...(有關這個去做...的策略

In the financial report (在這份財務報告裏...
For the financial report tells us...(由於這份財報告告訴我們...