verification that simplification in textbook is incorrect

Question

I am using a textbook that asks for the following expression to be simplified:

${9vw^3 - 7v^3w - vw^2}$

The answer given is:

${8vw^2 - 7v^3w}$

which seems wrong because I did not think you could subtract 2 similar terms with different polynomials.

Answer 1

The answer given is wrong: $9vw^3$ and $-vw^2$ are not like terms, so they cannot be added to make a single term. Maybe the problem was supposed to be $9vw^2 - 7v^3w - vw^2$?