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x in (-oo:+oo)
51/70 = x+3/10 // - x+3/10
51/70-x-(3/10) = 0
51/70-x-3/10 = 0
3/7-x = 0 // - 3/7
-x = -3/7 // * -1
x = 3/7
x = 3/7
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