Correct Answer: A

Rationale: The phrase 'thrice a number' translates to 3x, and 'twelve less than' means subtracting 12 from it. Therefore, the correct expression is 3x-12. Choice B, '12-3x', represents '12 less than a number thrice,' which is the opposite of the given phrase. Choice C, '3-12x', does not correctly interpret the phrase provided. Choice D, '12x-3', represents 'a number thrice less than twelve,' which is not the same as the original phrase.

Correct Answer: B

Rationale: The independent variable in this scenario is 'Stocks.' An independent variable is the one that is manipulated or controlled by the experimenter. In this case, stocks are the factor that is changing and influencing the other variables - production, sales, and investments. Production, sales, and investments are dependent on the changes in stocks; hence, they are the dependent variables. While production, sales, and investments may increase as a result of changes in stocks, the stocks themselves are the driving force behind these changes, making them the independent variable.

Correct Answer: C

Rationale: To convert 2.5 teaspoons of vanilla to milliliters, you multiply by the conversion factor: 2.5 teaspoons * 4.93 mL = 12.325 mL. Therefore, the correct amount of vanilla in milliliters is 12.325 mL. Choice A (5.33 mL) is incorrect because it does not account for the correct conversion factor. Choice B (7.43 mL) is incorrect as it also does not use the accurate conversion factor. Choice D (0.507 mL) is incorrect as it represents a miscalculation of the conversion.

Correct Answer: D

Rationale: The scatter plot illustrates the relationship between students' exam scores and heights. There is no correlation between these variables, as height is not expected to have a direct impact on exam scores. Therefore, choice D, 'No correlation,' is the correct answer. Choices A, 'Positive,' and C, 'Negative,' are incorrect because the scatter plot does not indicate a positive or negative correlation between exam scores and heights. Choice B, 'Positive and Negative,' is also incorrect because the scatter plot does not exhibit both positive and negative correlations simultaneously.

Correct Answer: A

Rationale: The correct expression for the sum of three times a number and eight times a different number is given by 3x + 8y. This represents adding three times the variable x (3x) to eight times the variable y (8y). Choice B (8x + 3x) is incorrect as it represents adding eight times x to three times x, which is redundant. Choice C (3x - 8y) is incorrect because it represents subtracting eight times y from three times x, not their sum. Choice D (8x - 3y) is also incorrect as it represents subtracting three times y from eight times x, not their sum.