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k in (-oo:+oo)
7/8-(6*k) = (-5/7)*k+303/8 // - (-5/7)*k+303/8
7/8-(6*k)-((-5/7)*k)-(303/8) = 0
(5/7)*k-6*k+7/8-303/8 = 0
-37/7*k-37 = 0 // + 37
-37/7*k = 37 // : -37/7
k = 37/(-37/7)
k = -7
k = -7
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