#### Answer

$$-5x^{\frac{2}{3}}$$

#### Work Step by Step

Given that the two expressions, $f(x)$ and $g(x)$ are functions, we know that they will follow the rules of functions listed on page 429. Knowing this, we obtain:
$$(-2+7)x^{\frac{2}{3}}=-5x^{\frac{2}{3}}$$