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a in (-oo:+oo)
3/8-3*a = -((3/4)*a)-39/40 // + -((3/4)*a)-39/40
(3/4)*a-3*a+3/8-(-39/40) = 0
(3/4)*a-3*a+3/8+39/40 = 0
27/20-9/4*a = 0 // - 27/20
-9/4*a = -27/20 // : -9/4
a = -27/20/(-9/4)
a = 3/5
a = 3/5
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