$\"\"$

The word $\"\"$ sum $\"\"$ means addition operation and its symbol $\"\"$ .

The word $\"\"$ the opposite of $\"\"$ $\"\"$ represents $\"\"$ .

The word $\"\"$ the additive inverse of $\"\"$ $\"\"$ represents 18 ( $\"\"$ ).

The word $\"\"$ The sum of the opposite of $\"\"$ (18) and its additive inverse (18) $\"\"$ represents $\"\"$ .

The expression is $\"\"$ . $\"\"$

The value of the expression is $\"\"$ .