Brianna's teacher asks her which of these three expressions are equivalent to each other. Expression A: 9x - 3x - 4 Expression B

: 12x - 4 Expression C: 5x + x - 4 Brianna says that all three expressions are equivalent because the value of each one is - 4 when x = 0. Brianna's thinking is incorrect. Identify the error in Brianna's thinking. Determine which of the three expressions are equivalent. Explain or show your process in determining which expressions are equivalent in the space provided.