Answer
$\text{Domain}=\{w|0\leq w\leq 10\}$
$\text{Range}=\{M|0\leq M\leq 300\}$
Work Step by Step
We are given the function modeling the number of minutes on the card after $w$ weeks:
$$M(w)=-30w+300.$$
The domain of the function represents the number of weeks in which you still have minutes on the card, so its low limit is $0$ and its top limit is obtained by solving the equation
$$M(w)=0$$
Solve the equation:
$$\begin{align*}
-30w+300&=0\\
30w&=300\\
w&=10.
\end{align*}$$
So the domain is:
$$\text{Domain}=\{w|0\leq w\leq 10\}.$$
The range of the function is the number of minutes, which is initially $300$ and decreases until it reaches $0$:
$$\text{Range}=\{M|0\leq M\leq 300\}.$$
Graph the function:
