how it's answer is 36?

Answer 1

This is not defined.

You can find the Committee Draft from May 6, 2005 of the C-standard here (pdf)

See section 6.5 Expressions:

2 Between the previous and next sequence point an object shall have its stored value modified at most once by the evaluation of an expression. Furthermore, the prior value shall be read only to determine the value to be stored.

and the example:

71) This paragraph renders undefined statement expressions such as

i = ++i + 1;

a[i++] = i;

Answer 2

The answer is actually undefined.

Answer 3

Answer in undefined because you've got some situations in which the parser doesn't know how to parse the code..

is a+++b: a + ++b or a++ + b?

Think the fact that usually white space is just ignored when lexing the source code. It may depends upon implementation of the compiler (and some other languages with same ++ operators may choose to give priority to one instead of another) but in general this is not safe.

For example in Java your code line gives 37 as the answer, because it chooses to bind ++ operators in a specific way according to precedence, but it's just a choice..

Answer 4

I ran this code in c# (.net framework 4) and the answer was 37 :)