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a in (-oo:+oo)
323/28 = 4*a+(5/7)*a+8 // - 4*a+(5/7)*a+8
323/28-(4*a)-((5/7)*a)-8 = 0
(-5/7)*a-4*a+323/28-8 = 0
99/28-33/7*a = 0 // - 99/28
-33/7*a = -99/28 // : -33/7
a = -99/28/(-33/7)
a = 3/4
a = 3/4
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