Problem: Define the operation "∘\circ∘" by x∘y=4x−3y+xyx \circ y=4 x-3 y+x yx∘y=4x−3y+xy, for all real numbers xxx and yyy. For how many real numbers yyy does 3∘y=12?3 \circ y=12?3∘y=12?
Answer Choices:
A. 000
B. 111
C. 333
D. 444
E. more than 444
Solution:
Substituting 333 for xxx yields 3∘y=12−3y+3y=123 \circ y=12-3 y+3 y=123∘y=12−3y+3y=12. Thus 3∘y=123 \circ y=123∘y=12 is true for all real numbers yyy.