Starting with 3x + x = 2x + 2y, simplify step by step: 4x = 2x + 2y, subtract 2x from both sides: 2x = 2y, divide both sides by 2: x = y. Therefore, statement D (x = y) is correct. Statements A, B, and E are false. Statement C is false because we CAN determine the relationship - x equals y.