To simplify the expression 2/1 + 5/4 - 2/1 + 5/4, we need to find a common denominator for all four fractions before adding or subtracting them. The common denominator for 2/1 and 2/1 is 1, since both fractions already have the same denominator. The common denominator for 5/4 and 5/4 is 4, since both fractions already have the same denominator. Therefore, the simplified expression is: 2/1 + 5/4 - 2/1 + 5/4 = (2 + 5)/1 + (5 + 5)/4 = 7/1 + 10/4 = 7 + 10/4 = (7*4 + 10)/4 = (28 + 10)/4 = 38/4 = 19/2

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