Correct Answer: A

Rationale: To multiply fractions, you multiply the numerators to get the new numerator and multiply the denominators to get the new denominator. Therefore, multiplying 2/3 by 3/4 results in (2*3) / (3*4) = 6/12. Simplifying 6/12 by dividing both the numerator and denominator by 6 gives 1. Hence, the correct answer is 1. Choices B, C, and D are incorrect as they do not represent the correct product of multiplying 2/3 by 3/4.

Correct Answer: A

Rationale: The expression x^2 - y^2 is a difference of squares, which follows the identity: x^2 - y^2 = (x + y)(x - y). Therefore, the given expression becomes: (x^2 - y^2) / (x - y) = (x + y)(x - y) / (x - y). Since (x - y) appears in both the numerator and the denominator, they cancel each other out, leaving x + y. Thus, the simplified form of (x^2 - y^2) / (x - y) is x + y. Therefore, the correct answer is A (x + y). Option B (x - y) is incorrect as it does not result from simplifying the given expression. Option C (1) is incorrect as it does not account for the variables x and y present in the expression. Option D ((x + y)/(x - y)) is incorrect as it presents the simplified form in a different format than the correct answer.

Correct Answer: B

Rationale: The correct answer is B: 'Positive number.' When you subtract one negative number from another negative number, the result can be a positive number. For example, the difference between -5 and -3 is 2, which is a positive number. Choice A, 'Negative number,' is incorrect because the result of subtracting two negative numbers can be positive. Choice C, 'Zero,' is incorrect because the difference between two negative numbers is not always zero. Choice D, 'Not enough information,' is incorrect because there is enough information to determine that the difference between two negative numbers can be a positive number.

Correct Answer: D

Rationale: The formula for the area of a square is given by the square of its side length: Area = side side. For this problem, the side length of the square is 75 centimeters. To find the area, you multiply 75 by itself: 75 75 = 5,625 square centimeters. Thus, the area of the square is 5,625 cm². This shows that option D is correct. Choices A, B, and C are incorrect as they do not correspond to the correct calculation of the area of a square with a side length of 75 centimeters.

Correct Answer: B

Rationale: From Equation 1: 2x + y = 0. Solve for y: y = -2x. Substitute y = -2x into Equation 2: x - 2(-2x) = 8. Simplify to x + 4x = 8, then 5x = 8, and x = 8 · 5 = 1.6. Substitute x = 1.6 back into y = -2x to find y = -3.2. Therefore, one solution is (1.6, -3.2). To find the second solution, use -1.6 for x to get (-1.6, 3.2). Thus, the correct answer is B, representing the solutions (1.8, -3.6) and (-1.8, 3.6). Choices A, C, and D contain incorrect values that do not match the solutions derived from solving the system of equations.