1. Stating the problem: Simplify the expression $9 - 21 \div (-7) + 7$. 2. Recall the order of operations: division and multiplication are performed before addition and subtraction. 3. Perform the division first: $$21 \div (-7) = -3$$ 4. Substitute back into the expression: $$9 - (-3) + 7$$ 5. Simplify the subtraction of a negative number: $$9 + 3 + 7$$ 6. Add the numbers step-by-step: $$9 + 3 = 12$$ $$12 + 7 = 19$$ 7. Final answer: $$19$$