Correct Answer: A

Rationale: To subtract 7 7/10 from 3 4/5, first convert 3 4/5 to have the same denominator as 7 7/10. Converting 4/5 to 8/10, the subtraction becomes 7 7/10 - 3 8/10. Subtracting, 7 - 3 = 4 and 7/10 - 8/10 = -1/10. Therefore, the result is 3 4/5 - 7 7/10 = 3 9/10. Choices B, C, and D are incorrect because they do not reflect the correct subtraction of fractions and whole numbers in this scenario.

Correct Answer: B

Rationale: When multiplying a positive integer by a negative integer, the product will always be negative. This is a fundamental rule of arithmetic. The sign of the product is determined by the rule that states a positive number multiplied by a negative number results in a negative number. Therefore, the statement that the product will always be negative is always true when multiplying positive and negative integers. Choice A is incorrect because the product is not always positive when multiplying positive and negative integers. Choice C is incorrect because the product is not dependent on the specific numbers but on the signs of the integers being multiplied. Choice D is incorrect as positive and negative integers can be multiplied.

Correct Answer: A

Rationale: To find the total weight of the delivery, you need to multiply the number of boxes (36) by the weight of each box (2.5 pounds). This gives you 36 boxes * 2.5 pounds = 90 pounds, which is the correct answer. Choice B (75 pounds), C (120 pounds), and D (100 pounds) are incorrect because they do not correctly calculate the total weight based on the given information.

Correct Answer: A

Rationale: 1/2 oz of perfume is equal to approximately 15 mL. To convert ounces to milliliters, we need to know that 1 oz is approximately 30 mL. Therefore, half an ounce, which is 1/2 oz, would be half of 30 mL, which equals 15 mL. Choice B, 20 mL, is incorrect as it does not correspond to the conversion factor of 1 oz to 30 mL. Choice C, 10 mL, is incorrect as it is half of the actual value. Choice D, 50 mL, is incorrect as it is the value of 1 oz rather than half an ounce.

Correct Answer: C

Rationale: To find x, set up the proportion and solve for x: 120/x = 40/0.5. Cross multiply to get 120 * 0.5 = 40x. This simplifies to 60 = 40x. Divide by 40 to isolate x, giving x = 60/40 = 1. Therefore, the correct answer is C, which is 1. Choice A (60) is incorrect because it does not match the correct calculation. Choice B (0) is incorrect as the calculation results in x = 1, not 0. Choice D (25) is incorrect as it does not match the correct calculation of x = 1.