Answer
The $x-intercepts$ are $+3$ and $-3$.
Work Step by Step
$$\frac{x^2}{9}+\frac{y^2}{4}=1$$
Set $y=0$
$$\frac{x^2}{9}+\frac{y^2}{4}=1$$ $$\frac{x^2}{9}+\frac{0^2}{4}=1$$ $$\frac{x^2}{9}+0=1$$ $$\frac{x^2}{9}=1$$
Multiply both sides by $9$
$$\frac{x^2}{9}(9)=1(9)$$ $$x^{2}=9$$
Get the square root of both terms
$$\sqrt (x^{2}) = \sqrt 9$$
Thus the $x-intercepts$ are $+3$ and $-3$.