Final answer:
The expression 7uv²+9w³ is already simplified because it contains no like terms to combine; like terms have the same variables and exponents and can be combined by adding or subtracting their coefficients.
Step-by-step explanation:
To simplify variable expressions involving like terms, one must combine those like terms. Looking at the expression 7uv²+9w³, it is clear that there are no like terms to combine since they contain different variables and powers. Therefore, the expression is already in its simplest form. When simplifying expressions, if terms have the exact same variable and exponent, then you can combine them by adding or subtracting the coefficients.
For instance, if you were given the expression 3a² + 2a², you could combine the like terms (since they both have the variable 'a' raised to the second power) to get 5a².
Remember to also check the answer to ensure it makes sense with respect to the original problem and the mathematical rules that apply.