I know how to solve the questions but I want to know the original source of the questions.
You've asked something similar on another thread!
Apart from the fact that knowing the "original source" of a question isn't much help in solving it, most maths questions (at least at school level) don't have an "original source" - most question setters will take an existing question, modify the numbers or some slight phrasing of the question, and construct a new question based on an earlier one.
This isn't terribly unreasonable, since when you're first starting out with a topic in mathematics you need lots of practice with a particular technique to ensure that you're comfortable with it, not lots of wildly different questions that may just confuse you