Find The Difference Of 12x - 9x ?, A. 3x , B. 2x , C. -2x , D. -3x

Find the difference of 12x – 9x ? 
A. 3x
B. 2x
C. -2x
D. -3x

 

Answer:

A. 3x

Step-by-step explanation:

Since 12x and 9x are both "like terms" (both contain x-variables), they can easily be combined (added, subtracted, multiplied, divided, etc.).

Therefore, 12x - 9x is literally a simple matter of taking 12 and subtracting 9 from it.

12x - 9x = 3x

BUT if the algebraic equation was, for example, 12x - 9y, we would NOT be able to combine these two terms together in any way, since they are NOT "like terms" (they have different variables - as one has an x-variable, and the other has a y-variable).