$\"\"$

The expression is $\"\"$ .

$\"\"$ (Substitute x = – 3, y = 8 and z = – 12 in original expression) $\"\"$

Additive inverse of – 8 is 8.

To subtract – 8, add 8.

$\"\"$

$\"\"$ (Add: $\"\"$ ) $\"\"$

Additive inverse of – 3 is 3.

To subtract – 3, add 3.

$\"\"$

$\"\"$ (Add: $\"\"$ ) $\"\"$

The simplified expression is – 17.