The slope tells how much the total cost changes for each additional mile. Using the two points, the slope is

So the graph shows that the cost increases by \2$permiletraveled.$

Substitute $x=0$ into the equation: $y=4(0)-3=-3$. So the $y$-coordinate is $-3$.

Starting with $y=-3x+5$, add $3x$ to both sides to move the $x$-term to the left: $3x+y=5$. This is in standard form $Ax+By=C$, and the coefficient of $x$ is positive.

A point is on the graph if its coordinates make the equation true. Substituting $x=0$ into $y=3x-2$ gives $y=3(0)-2=-2$, so $(0,-2)$ is on the line.

Because the function is linear, its rate of change is constant. From $x=-2$ to $x=1$, $x$ increases by $3$ while $f(x)$ decreases by $6$, so the slope is $\frac{-6}{3}=-2$. This matches the change from $x=1$ to $x=4$ as well. From $x=4$ to $x=7$, $x$ increases by $3$, so $f(x)$ must decrease by $2(3)=6$. Since $f(4)=-1$, we get $f(7)=-1-6=-7$.