Question 1020794
From the given, a+bi = a+3i, and e+fi = a-c+fi.  Together with c+di, their sum is 2a+(3+d+f)i.  This sum is supposed to be equal to 2i.

Therefore, a = 0 and 3+d+f = 2, and by transposition,

{{{highlight(d+f = -1)}}}.