Which expression is not equivalent to 8 ∙ x ∙ 2 ∙ y? 1. 8x + 2y 2. 16yx 3. 16xy

The answer is:  "Answer choice: 1):  "8x + 2y".

   Note:  " 8 * x * 2 * y = 16xy ".  

So, choice 3):   "16xy is correct". 

Choice 2):  "16yx" is also correct, since:  "16xy = 16yx".

Choice 1)": is incorrect, so this is the incorrect answer.

to  be sure.  let's plug in a values, "3" for "x" ; and "4" for "y"; 

Choice 1) " 8x + 2y"  ;    8(3) + 2(4) = 24 +8 = 32 .

Now, try:  "16xy".  16(3)(5) = 48(5) = 240.   

Note that:  "32≠40" .

So, Choice 1):   "8x + 2y" ;  is the correct answer.