Simple problem with phasors
So yo had the denominator wrong as it should have been -7 + j17 instead of -6 + j17. I don't quite see the point of converting it back and forth between Cartesian and polar forms; you can calculate it directly will less work; and obviously (-3*5)+4+4=-7.

Your error however is a lot more trivial than that, you carried over a 4 to a 5: