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(1/2)*x-((6/7)*x)-3 = -87/14 // + -87/14
(1/2)*x-((6/7)*x)-(-87/14)-3 = 0
(-6/7)*x+(1/2)*x+87/14-3 = 0
45/14-5/14*x = 0 // - 45/14
-5/14*x = -45/14 // : -5/14
x = -45/14/(-5/14)
x = 9
x = 9
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