I was doing a practice problem. I calculated the correct value for i_a = -2.4 A. But I used KVL on the bottom loop to get R, and got the inverse of the answer that I actually needed. My equation was -5*ia - 6V + 18*-6R = 0. There is no current flow from the current source above to the loop below.
According to the solutions, I needed to use voltage division to get the correct answer, but I was wondering why is this the case? I could get the correct solution with current division but I don't get why KVL doesn't work for this loop.