1. State the problem: Simplify the expression $$(-7a - 19c) - (-12a + 30c) - (-21a - 11c)$$. 2. Remove parentheses by distributing the minus signs: $$-7a - 19c + 12a - 30c + 21a + 11c$$ 3. Combine like terms: For $a$: $$-7a + 12a + 21a = ( -7 + 12 + 21 )a = 26a$$ For $c$: $$-19c - 30c + 11c = ( -19 - 30 + 11 )c = -38c$$ 4. Final simplified expression: $$26a - 38c$$