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X in (-oo:+oo)
42/15 = X/255 // - X/255
42/15-(X/255) = 0
14/5-1/255*X = 0 // - 14/5
-1/255*X = -14/5 // : -1/255
X = -14/5/(-1/255)
X = 714
X = 714
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