If you learn latex, then you will get answers a lot quicker. A quick search on google should get you started along with [*tex][*/tex] boxes. I'm assuming by Q[x] you mean rational numbers, but I don't know what you mean by "Z3[x]" In your own words, explain what it means

We are asked whether or not is true in the space of rational numbers.

If this were true then divides the difference with a rational quotient and no remainder.

Use polynomial long division to verify whether or not it is the case.

If I'm missing something, let me know.