Brianna’s teacher asks her which of these three expressions are equivalent to each other.

Expression A:
9
x
−
3
x
−
4
Expression B:
12
x
−
4
Expression C:
5
x
+
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.