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a in (-oo:+oo)
(3/7)*a+2/5 = a+254/35 // - a+254/35
(3/7)*a-a+2/5-(254/35) = 0
(3/7)*a-a+2/5-254/35 = 0
-4/7*a-48/7 = 0 // + 48/7
-4/7*a = 48/7 // : -4/7
a = 48/7/(-4/7)
a = -12
a = -12
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