I gave algebra this problem as an opener today.
One period was convinced it had to be one of these three possibilities.
The class was split into thirds when I took a poll on 1, 2, or 3. We talked about what x actually represented and decided to use x = 3 as a test value.
Students were surprised with their results after plugging 3 in for x. I kept saying “If only there were a way to add to over and over without having to do all that work”.
At time time of the year, students get so caught up in multiplying polynomials, finding GCFs, and dealing with exponents that they get tunnel vision and sometimes apply ideas in inappropriate situations. This opener helped put on the breaks.