If I am combining functions to construct a big formula, how to determine its arrangements?

Hi,
Excel has several built-in functions like sum, count ...etc.
Sometimes I need to combine several built-in functions to perform a big formula.
My question is, how do we determine the arrangements of the built-in functions?
For example, I was reading this article regarding removing several characters from a cell:
https://www.wps.com/blog/how-to-remo...asiest-ways-1/, and there are several other examples.
They used the combined LEFT & LEN - RIGHT & LEN in the following order:

Formula:

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Formula:

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My exact question is, how do you determine which function to start with?
Is there any rule to master such behavior?
Using RIGHT/LEFT then use LEN, does it matter if I started with LEN and then LEFT/RIGHT?
I hope that I was able to express myself and sorry for my English.

You have 365, so use TEXTBEFORE and TEXTAFTER instead.

Thanks for the fast reply.
That was just an example, but I was refer to the concept away from the example details.
So how to determine the order?

In your examples, you need to extract text from an existing string. So, the basic functions are LEFT and RIGHT. If the length of the string is known, you could just subtract 1 from it to get the length of the text to be extracted. BUT, if the length of the string is variable, you use LEN to determine that value and subtract 1 from that instead.

The rule of thumb is to start with the simple function (LEFT or RIGHT) to test the formula. Then embellish it to make it more flexible.

With 365, you have the LET function which allows you to define and set variables which can make the formula easier to read, less repetitive, and more efficient (and shorter).