Operator Precedence : 

Arithmetic Operators are evaluvated left to right using the precedence of operator when the expression is written without the paranthesis.They are two levels of arithmetic operators in C. 1 : High Priority * / % 2 : Low Priority + -. Arithmetic Expression evaluation is carried out using the two phases from left to right.
Rules for Evaluation of Expression : 

1 : Evaluate the sub-expression from left to right. If parenthesized. 

2 : Evaluate the arithemetic Expression from left to right using the rules of precedence. 

3 : The highest precedence is given to the expression with in paranthesis. 

4 : When parantheses are used, the expressions within parantheses assume highest priority. 

5 : Apply the associative rule, if more operators of the same precedence occurs.