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.
Have a great day!!!!