$\"\"$

The expression is $\"\"$ .

$\"\"$ (Substitute a = – 3, b = 8 and c = – 12)

$\"\"$ (Apply commutative property of addition: $\"\"$ ) \ \ $\"\"$

Additive inverse of – 3 is 3. To subtract 3, add – 3.

$\"\"$

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

Additive inverse of – 12 is 12. To subtract – 12, add 12.

$\"\"$

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

The simplified expression is 17.