The correct answer for the question that is being presented above is this one:
Identity refers to equation if left and right equation are the same; Contradiction on the other hand, refers to dissimilar left and right equation.
(1) 8x + 24 = 2(4x + 12) => Identity
(2) 5x + 18 - x = 2(2x + 8) => Contradiction
(3) 7(3x - 2) = 20x - 13 => Contradiction
(4) 3x + 2(x - 10) = 5(x - 4) =>Identity