Correct Answer: D

Rationale: To find the result of subtracting 8.4 from 3.7, you need to subtract 3.7 from 8.4. Performing this subtraction, 8.4 - 3.7 equals 4.7. Therefore, the correct answer is 4.7. Choice A, 4.5, is incorrect as it is not the result of subtracting 8.4 from 3.7. Choices B and C, 4.8 and 4.6 respectively, are also incorrect as they do not match the correct subtraction result of 4.7.

Correct Answer: B

Rationale: To find the total number of shipping labels needed, multiply the number of boxes by the labels per box: 9 boxes * 3 labels per box = 27 labels. Therefore, the worker needs 27 shipping labels each day. Choice A, 24 labels, is incorrect because it results from multiplying 9 boxes by 3 labels without calculating the correct total. Choice C, 20 labels, is incorrect as it underestimates the total number of labels needed. Choice D, 30 labels, is incorrect as it overestimates the total by multiplying incorrectly.

Correct Answer: D

Rationale: To convert ounces to pounds, you divide the number of ounces by 16 since there are 16 ounces in a pound. Therefore, 176 ounces · 16 = 11 pounds. Choice A is incorrect because it miscalculates the conversion. Choices B and C are also incorrect as they do not accurately convert the given ounces to pounds.

Correct Answer: D

Rationale: To express the repeating decimal 0.7777... as a fraction, let x = 0.7777... Multiplying both sides by 10 to shift the decimal point to the right gives: 10x = 7.7777... Subtracting the original equation from the new equation eliminates the repeating decimal: 10x - x = 7.7777... - 0.7777... 9x = 7 x = 7/9. Therefore, the decimal 0.7777... can be expressed as the fraction 7/9. Choices A, B, and C are incorrect as they do not accurately represent the decimal 0.7777... when converted to a fraction.

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.