associativity of operators in C language

Hello friends,

First of all I would like to say that although I have initiatiated this thread in "engineering concepts" forum, but I thing it should be here, please forgive me for this.

I am following Let us C, 6th edition, by Yashavant Kanetkar,
I have a problem understanding the concept of associativity of operators,

I tried to find some good material on internet by searching in google but could not find much.

Kanetkar writes,

"Left to Right associativity means that the left operand must be unambiguous. Unambiguous in what sense? It must not be involved in evaluation of any other sub-expression. Similarly in case of Right to Left associativity the right operator must be unambiguous."

I could not understand what it means by "being unambiguous".

There is a expression,

g = 10/5/2/1

Now we have to find the order in whcih the calculations will take place
In his solution book, he gives the solution using a table like this.

Code:

 operator            left operand               Right operand                         Remark
     
1st     /               10                        5 or 5/2/1               Left operand is unambiguous,
                                                                                            Right is not

2nd   /               10/5 or 5                   2 or 2/1             Left operand is unambiguous,
                                                                                             Right is not

3rd   /               10/5/2 or 2                1                       Right operand is unambiguous,
                                                                                            Left is not

next he says
"operation will be performed first which has an unambiguous left operand.
evaluation order will be:

10/5/2/1
2/2/1
1/1
1
"

My questions are:

1) in first row and right column why he writes only two operands that are possible: 5 or 5/2/1 why also not 5/2


2) In the second row in the remark column why he says that left operand is unambiguous when there are two operands that are possible i.e. 10/5 or 5.

3) If two '/' has left operand as unambiguous (assuming that what he is saying in row 2 is correct) , how he solved the problem. I mean how he decided that first operatoe '/' will be evaluated first.

Thanks a lot friends.