1)

19/27 - x - 10/27 = 2/27

9/27 - x = 2/27

x = 9/27 - 2/27

x = 7/27

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2)

8/15 + x = 8/15

x = 8/15 - 8/15

x = 0

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3)

5/9 + x = 7/9

x = 7/9 - 5/9

x = 2/9

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