Correct Answer: A

Rationale: To subtract fractions, find a common denominator. The common denominator for 6 and 4 is 12. So, 5/6 = 10/12 and 3/4 = 9/12. Subtracting 10/12 - 9/12 gives us 1/12 as the result. Choice A, 1/12, is the correct answer because it represents the simplified result of subtracting the fractions with the common denominator. Choices B, C, and D are incorrect because they do not reflect the correct subtraction result of 1/12 after finding the common denominator.

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: A

Rationale: To multiply the fractions, convert the mixed numbers to improper fractions: 1 4/5 = 9/5. Then, multiply the fractions: (4/9) (9/5) (2/5) = 8/25. The correct answer is A. Choice B is incorrect as it does not match the result of the multiplication. Choice C is incorrect as it is not the result of multiplying the fractions. Choice D is incorrect as it is not the result of the given multiplication.

Correct Answer: A

Rationale: To convert ounces to pounds, you need to know that there are 16 ounces in a pound. Therefore, to find how many pounds are in 80 ounces, you divide 80 by 16, which equals 5 pounds. Thus, the correct answer is 5 pounds. Choice B, 6 pounds, is incorrect because it doesn't accurately reflect the conversion from ounces to pounds. Choice C, 4 pounds, and Choice D, 3 pounds, are also incorrect as they do not align with the correct conversion factor of 16 ounces to 1 pound.

Correct Answer: A

Rationale: To convert liters to milliliters, remember there are 1,000 milliliters in a liter. So, to find how many milliliters are in 5 liters, you multiply 5 (liters) by 1,000 (milliliters per liter), which equals 5,000 milliliters. Choice A is correct as it converts 5 liters to milliliters accurately. Choice B, 50 milliliters, is incorrect as it mistakenly converts liters to milliliters by a factor of 100 instead of 1,000. Choice C, 500 milliliters, is incorrect as it also wrongly converts liters to milliliters by a factor of 10 instead of 1,000. Choice D, 0.5 milliliters, is incorrect as it inaccurately converts 5 liters to 0.5 milliliters, which is not correct.