Correct Answer: A

Rationale:
To find the average speed, first, convert 45 minutes to hours (45/60 = 0.75 hours).
Then, divide the distance by the time: 5 miles · 0.75 hours = 6.67 mph.
Choice A is correct because it accurately calculates the average speed based on the distance covered and time taken.
Choice B is incorrect as it does not consider the time taken to cover the distance.
Choice C is incorrect as it is higher than the calculated speed.
Choice D is incorrect as it is higher and does not match the calculated average speed.

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: D

Rationale:
To find the distance traveled, multiply the speed of 70 mph by the time of 6 hours: 70 mph 6 hours = 420 miles.
Therefore, the correct answer is 420 miles.

Choices A, B, and C are incorrect as they do not result from the correct calculation.

Correct Answer: D

Rationale:
To convert kilograms to grams, you multiply by 1,000 since there are 1,000 grams in a kilogram.
Therefore, 8 kilograms = 8 x 1,000 = 8,000 grams. The correct answer is 8,000 grams, which is option D.

Choices A and C are incorrect as they incorrectly multiply by 10,000 instead of 1,000.
Choice B is incorrect as it divides 8 by 10 instead of multiplying by 1,000.

Correct Answer: B

Rationale:
To convert a fraction to a decimal, divide the numerator by the denominator. In this case, 1 · 5 = 0.2.
Therefore, the correct answer is B.
Choice A (0.5) is incorrect because the decimal form of 1/5 is not 0.5.
Choice C (1.5) is incorrect as it is the sum of 1 and 0.5, not the decimal form of 1/5.
Choice D (0.15) is incorrect as it is the decimal form of 15/100, not 1/5.