Correct Answer: A

Rationale: To convert the improper fraction 18/5 to a mixed number, divide 18 by 5. The quotient is 3 with a remainder of 3, which translates to 3 3/5. Therefore, the correct answer is A. Choices B, C, and D are incorrect because they do not accurately represent the conversion of 18/5 to a mixed number.

Correct Answer: D

Rationale: The slope of the equation y = 50x is 50, which means that for each additional gigabyte of data used, the cost increases by 50 dollars. Therefore, the interpretation of the slope is that it represents the cost per gigabyte, making '50 dollars per gigabyte' the correct answer. Choices A, B, and C are incorrect because they do not reflect the relationship between the cost and the amount of data used in the given equation.

Correct Answer: B

Rationale: Adding 0.75 and 0.625 gives: 0.75+0.625=1.375.

Correct Answer: A

Rationale: To divide fractions, you multiply the first fraction by the reciprocal of the second fraction. So, (4/3) · (9/13) = (4/3) * (13/9) = 52/27. This fraction is already in its reduced form, making choice A the correct answer. Choices B, C, and D are incorrect as they do not represent the correct result of dividing the fractions 4/3 by 9/13.

Correct Answer: D

Rationale: To convert the mixed number 8 3/7 to an improper fraction, multiply the whole number (8) by the denominator (7) and add the numerator (3) to get the numerator of the improper fraction. This gives us (8*7 + 3) / 7 = 59/7. Therefore, the correct answer is 59/7. Choice A (11/7), choice B (21/8), and choice C (5/3) are incorrect because they do not correctly convert the mixed number to an improper fraction.