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: B

Rationale: To find the sum of fractions with the same denominator, add the numerators. Here, 3/7 + 4/7 + 2/7 = (3 + 4 + 2)/7 = 9/7. Therefore, the correct answer is 9/7. Choice A (7/7) is incorrect as the sum is not 7/7. Choice C (6/7) is incorrect as the sum is not 6/7. Choice D (7/7) is incorrect as the sum is not 7/7.

Correct Answer: B

Rationale: To find the rate of calories burned per mile, divide the total calories burned by the total miles run: 2276 · 21.4 ≈ 106.4 calories per mile. This calculation gives the average number of calories burned for each mile of the marathon. Choice A, 107.5, is incorrect as it does not match the precise calculation result. Choices C and D are also incorrect as they are not the accurate rate of calories burned per mile based on the given data.

Correct Answer: B

Rationale: Rationale: 1. Calculate the excess blood sugar above 100mg/dL: 180mg/dL - 100mg/dL = 80mg/dL. 2. Determine the insulin dose based on the patient's usual insulin dose: 80mg/dL / 40mg/dL = 2 units. 3. Add the calculated insulin dose to the patient's usual insulin dose: 1 unit (usual dose) + 2 units (calculated dose) = 3 units. Therefore, the correct answer is 3 units of insulin should be administered to the diabetic patient with a blood sugar level of 180mg/dL.

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.