Correct Answer: B

Rationale:
To solve the equation 3x + 9 = 0, first, isolate the variable x. Subtract 9 from both sides to get 3x = -9.
Then, divide by 3 to solve for x, giving x = -3.
Therefore, the correct answer is B.
Choice A, x = -3, is the correct solution.

Choices C and D are incorrect as they do not satisfy the equation when substituted back into it.

Correct Answer: A

Rationale:
To multiply fractions, multiply the numerators together and the denominators together. In this case, 3/4 1/3 = (3 1) / (4 3) = 3/12 = 1/4.
Therefore, the correct answer is A: 1/4.

Choices B (1/3), C (3/5), and D (3/8) are incorrect because they do not result from the correct multiplication of the given fractions.

Correct Answer: A

Rationale:
To subtract mixed numbers, find a common denominator. Converting 6 1/2 to 6 3/6 and 2 2/3 to 2 4/6, the calculation becomes 6 3/6 - 2 4/6 = 4 1/6.
Therefore, the correct answer is A.
Choice B (3 1/3) is incorrect as the correct result is not an improper fraction.
Choice C (3 5/6) is incorrect as it does not represent the result of the subtraction.
Choice D (4 1/3) is incorrect as it does not match the correct calculation.

Correct Answer: B

Rationale:
To convert ounces to milliliters, multiply the number of ounces by 29.5735. 3/4 oz 29.5735 ≈ 22.5 mL.
Therefore, the correct answer is 22.5 mL.
Choice A (25 mL) is incorrect as it does not result from the correct conversion.

Choices C (15 mL) and D (20 mL) are also incorrect conversions.

Correct Answer: A

Rationale:
To multiply the fractions, convert the mixed numbers to improper fractions: 1 4/5 = 9/5.
Then, multiply the fractions: (4/9) (9/5) (2/5) = 8/25. The correct answer is A.
Choice B is incorrect as it does not match the result of the multiplication.
Choice C is incorrect as it is not the result of multiplying the fractions.
Choice D is incorrect as it is not the result of the given multiplication.