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a in (-oo:+oo)
7-((2/5)*a) = 7*a+331/5 // - 7*a+331/5
7-((2/5)*a)-(7*a)-(331/5) = 0
(-2/5)*a-7*a-331/5+7 = 0
-37/5*a-296/5 = 0 // + 296/5
-37/5*a = 296/5 // : -37/5
a = 296/5/(-37/5)
a = -8
a = -8
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