75 * 1000/3600 = 20.8333333
You just need to multiply with 1000 to get m from km and divide by 3600 because you are converting hours in seconds.
First, you have to get the equation to the normal form of a line. To do this, you divide both sides by -6 to get

. The y-intercept is at -4 and your slope is 2/3. Use this to graph the equation.
The apothem of this is 13