(a+b) +5i=9+ai what is the value of b

To starting to solving their equation of b. First to add -a to both sides.  Put a+b+5i+−a=ai+9+− a, and it equals to b+5i=ai−a+9. Finally, then add negative 5i to the both sides. Put b+5i+−5i=ai−a+9+−5i, and finally put b=ai−a−5i+9.

Answer is b=ai-a-5i+9.

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Ithink it is 7. 16