Answer
$y=30-3x$
$y$-intercept: $30$
The line falls
Work Step by Step
The remaining money on the card is the difference between the initial amount ($\$30$) and the amount spent on $x$ smoothies:
$$y=30-3x.$$
If we graph the function, the $y$-intercept will be the value of $y$ for $x=0$:
$$y=30-3(0)=30.$$
So the $y$-intercept represents the initial amount of money on the card.
The graph of the function is a line which falls from left to right because the amount of money on the card decreases as smoothies are bought.
