1. Problem: Evaluate the expression $y^2 + 3y - 4$ when $y = 9$. 2. Formula and rules: To evaluate a polynomial at a given value, substitute the value for $y$ and follow the order of operations: exponents first, then multiplication, then addition and subtraction from left to right. 3. Substitute the value into the expression: $$9^2 + 3(9) - 4$$ 4. Compute the power and the product: $$81 + 27 - 4$$ 5. Combine the terms step by step: $$108 - 4$$ 6. Final value after subtraction: $$104$$ 7. Answer: The value of $y^2 + 3y - 4$ when $y = 9$ is $104$.