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a in (-oo:+oo)
-a-(3/8) = 61/8 // - 61/8
-a-(3/8)-(61/8) = 0
-a-3/8-61/8 = 0
-a-8 = 0 // + 8
-a = 8 // * -1
a = -8
a = -8
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