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90/7 = 6*x-(4*x)+6/7 // - 6*x-(4*x)+6/7
4*x-(6*x)+90/7-(6/7) = 0
4*x-6*x+90/7-6/7 = 0
12-2*x = 0 // - 12
-2*x = -12 // : -2
x = -12/(-2)
x = 6
x = 6
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