Group 1:[br]Correct:[math]\frac{\frac{x^2-y^2}{2}}{\frac{x-y}{4}}[/math][br][br]Incorrect: [math]\frac{w^2+2w+1}{\frac{w+1}{3}}[/math]

Group 2:[br]Correct: [math]\frac{\frac{p^2+7p}{3p}}{\frac{49-p^2}{3p-21}}[/math][br][br]Incorrect: [math]\frac{\frac{5a^2-20}{2a+2}}{\frac{10a-20}{4a}}[/math][br][br]

Group 3:[br]Correct: [math]\frac{\frac{2y}{y^2-4}}{\frac{3}{y^2-4y+4}}[/math][br][br]Incorrect: [math]\frac{\frac{c^2+2c-3}{3c+3}}{\frac{c^2+5c+6}{2c+2}}[/math]