-3j +4/6 = 12

-18j/6 +4/6 =12/6

-18j /6= 12/6- 4/6 = 8/6

-18j = 8

– j = 8/18 = 4/9

j = – 4/9

There problably was a problem in te way you wrote the equation in your post

well check both of the answers because the question was confusing so i wrote both the solutions.

Solution A

18j + 4 / – 6 = 12

18j + 4 = 12 x -6

18j + 4 = -72

18j = -76

j = -4.22

OR

Solution B

-3j + 4 = 12 x -6

-3j + 4 = -72

-3j = -76

j = -76 / -3 =25.33