Answer:
Expression A & Expression C are equivalent
Step-by-step explanation:
●In Expression A :-
9x - 3x - 4
=> 6x - 4 ( Substracting the like terms )
● In Expression C :-
5x + x - 4
=> 6x - 4 ( Adding like terms )
● In Expression B
12x - 4
Comparing all the expressions , we find both expression A & C have 5x - 4 as eqn. So they are equivalent.
Eqns are known as equivalent only when the final result will be equal after putting 'n' number of values in place of the variable. For example ,
expression A & C are equivalent. If we gonna take x = 1 , then the final result will be 6×1 - 4 = 2. Here we find that after putting x=1 in the expressions , the final result is equal in both the expressions & that is 2.
So the mistake of Brianna was her wrong assumption about equivalent expression.