3/7X + 11/14X = 5/12 - 3/4 6/14X + 11/14X = 5/12 - 9/12 17/14X = - 4/12 17/14X = - 2/6 X = - 2/6 : 17/14 = - 28/102 = - 14/51
6/14x+11/14x=-9/12+5/12; x=-79,1/3