The correct answer is Choice B.
Equate both expressions to find $b$.
Choices A, C, and D are incorrect and may result from algebraic mistakes.
✨ Expert's Tip ✨
An alternate method is to match the two expressions term-by-term, i.e.,$\frac{4}{x-\frac{b}{3}} = \frac{12}{3x-3b}$which looks very much like the 1st equation. Knowing that$\frac{12}{3x-9} = \frac{12}{3x-3b}$,$b=3$.