c+4/6=3c-2/7

с-3с=-2/7-4/6

-2с=-40/42

с=-40/42:(-2)

с=10/21

Проверяем: 10/21+4/6=3*10/21-2/7

                      1 1/7=10/7-2/7

                       1 1/7=1 1/7

Verified answer

с+4/6=3с-2/7 (множимо на 42,        6*7=42)

42с+28=126с-12

42с-126с=-12-28

-84с=-40

с= (-40) : (- 84)

с = 40/84= 10/21

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