#### Answer

Domain: $[-2,6]$
Range: $[-6, 18]$

#### Work Step by Step

We are given:
$f(x)=3x$, $-2\leq x\leq 6$
The domain consists of all values that $x$ is allowed to be. In this case, $x$ is restricted to fall between $-2$ and $6$, so the domain is: $[-2, 6]$.
The range consists of all values that $y$ can be. We find the extremes of $y$ by using the end points of $x$ (this works because the equation is a line):
$f(-2)=3(-2)=-6$
$f(6)=3(6)=18$
Thus the range is: $[-6, 18]$.