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a in (-oo:+oo)
-((5/7)*a)-a-5/9 = 613/63 // - 613/63
-((5/7)*a)-a-5/9-(613/63) = 0
(-5/7)*a-a-5/9-613/63 = 0
-12/7*a-72/7 = 0 // + 72/7
-12/7*a = 72/7 // : -12/7
a = 72/7/(-12/7)
a = -6
a = -6
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