Is there an easy way to extract partial css in element of html?

Many elements refer to many css and many css refer to many elements.

Is there a technique that is easiest to look at for an element of css?

For example:

I have a 1000 line html file and

I have a 1000 line css file

example i would like to know <div class = 'container'> and the inner element in line 574. Which css line is used?

Is there a method or tools that makes it easier or faster?