First we need to place the j on one side only
So we can move "j" from left to right, doing the opposite operation
[tex]6=-9+7j-4j[/tex]We can do the same for -9
[tex]6+9=7j-4j[/tex]We can operate the terms that have j and do the sum to the both sides
[tex]15=3j[/tex]Then, to leave
