Correct Answer: B

Rationale: The correct answer is B: Decimal. The decimal system, also known as the base-10 system, is the standard system for denoting integer and non-integer numbers in the United States and many other countries. In the decimal system, numbers are represented using 10 digits (0-9). Choices A, C, and D are incorrect. Tertiary, Napoleonic, and Binary number systems are not commonly used for general number representation in the United States.

Correct Answer: C

Rationale: To solve the equation 2x - 7 = 9, first, add 7 to both sides to isolate the variable: 2x = 16. Then, divide by 2 to solve for x: x = 8. Choice A (x = 10) is incorrect because the solution is x = 8, not 10. Choice B (x = 7) is incorrect as it does not correctly solve the equation. Choice D (x = 5) is incorrect as it does not yield the correct solution for x.

Correct Answer: C

Rationale: Rationale: The correct answer is obtained by applying the formula for the circumference of a circle, which is \(C = \pi \times d\), where \(d\) is the diameter of the circle. By substituting the given diameter of 40cm into the formula and performing the calculation, we find that the circumference of the pizza is 125.6cm.

Correct Answer: A

Rationale: To calculate the rate of calories burned per mile, divide the total calories burned by the total miles run: 2276 · 21.4 ≈ 106.4 calories per mile. The correct answer is A. Choice B, C, and D are incorrect as they do not match the correct calculation result. Therefore, they can be eliminated. It is essential to divide the total calories burned by the total miles run to determine the rate of calories burned per mile accurately.

Correct Answer: A

Rationale: To convert grams to milligrams, you need to multiply by 1,000 since there are 1,000 milligrams in a gram. So, 1,000 x 7 grams = 7,000 mg. This means that there are 7,000 milligrams in 7 grams. Choices B, C, and D are incorrect because they do not correctly convert grams to milligrams.