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(3/7)*x+3/7 = 6*x+216/49 // - 6*x+216/49
(3/7)*x-(6*x)+3/7-(216/49) = 0
(3/7)*x-6*x+3/7-216/49 = 0
-39/7*x-195/49 = 0 // + 195/49
-39/7*x = 195/49 // : -39/7
x = 195/49/(-39/7)
x = -5/7
x = -5/7
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