Correct Answer: A

Rationale: The student's score is calculated by adding the points earned for correct answers (x) and subtracting the points lost for incorrect answers (y/2). Therefore, the expression for the student's score on the exam is x - y/2. Option A is correct because it accurately represents this calculation. Option B (x - y) is incorrect as it does not account for the penalty of losing half a point for each incorrect answer. Option C (30 - (x + y)) is incorrect as it subtracts the total number of questions from the sum of correct and blank answers, which does not represent the scoring system. Option D (30 - x - y/2) is also incorrect as it incorrectly subtracts x from 30 and then deducts y divided by 2, which is not the correct scoring method for the exam.

Correct Answer: C

Rationale: To find the value of b in the equation 5b - 4 = 2b + 17, you need to first simplify the equation. By subtracting 2b from both sides of the equation and adding 4 to both sides, you get 3b = 21. Then, dividing both sides of the equation by 3 gives you b = 7. Therefore, the value of b is 7, which corresponds to option C. Choice A (13) is incorrect as it does not match the correct calculation. Choice B (24) is incorrect as it is not the result of the correct algebraic manipulation. Choice D (21) is incorrect as it is not the value of b obtained after solving the equation step by step.

Correct Answer: B

Rationale: When rounding 2678 to the nearest thousandth, you would look at the digit in the thousandth place, which is 7. To decide whether to round up or down, you consider the digit to the immediate right of the place you are rounding to. Since 7 is equal to or greater than 5, you round up. Choice A, ten-thousandth, is incorrect as we are rounding to the thousandth place. Choice C, hundredth, is not relevant as we are not rounding to that place value. Choice D, thousand, is incorrect as it is the original number being rounded, not the place value used for rounding.

Correct Answer: A

Rationale: The mean is calculated by summing all values in a dataset and then dividing by the total number of values. Outliers, which are data points significantly different from the other values, can greatly impact the mean because they affect the sum. The mean is sensitive to extreme values, making it the measure for the center of a small sample set most affected by outliers. The median, on the other hand, is not influenced by outliers as it represents the middle value when the data points are ordered. The mode is the value that appears most frequently in the dataset and is not directly influenced by outliers. Therefore, the correct answer is the mean, as it is highly influenced by outliers in a small sample set.

Correct Answer: C

Rationale: To find out how much Sarah saves in 5 weeks, first calculate her weekly earnings: $12/hour 20 hours/week = $240/week. Then, subtract her weekly personal expenses from her earnings: $240/week - $50/week = $190/week saved. Over 5 weeks, she will save $190/week 5 weeks = $950. However, none of the provided answer choices match $950. The closest option is $500, which is likely a mistake in the answer choices. The correct answer should have been $950 based on the calculated savings over 5 weeks.