That depends on what you want to "do" with it.
Before you can find an answer, you generally have to know
what the question is, and you may not be there yet.
One thing I can see that you might want to "do" with this equation is
find out what number ' i ' must be in order to make the equation true.
Here's how you might do that:
You said 3 + 10i = 4i - 18
Lets subtract 4i
from each side: 3 + 6i = - 18
Now subtract 3
from each side: 6i = - 21
Divide each side by 6 : i = - 21/6 or -(3 and 1/2) .