Graph the line using the slope and y-intercept, or two points.
Slope: 
−
1
-
1
Y-Intercept: 
−
2
-
2
x
y
0
−
2
1
−
3
Please mark BRAINLIEST ❤️
 
        
             
        
        
        
Check the picture below.
now, keep in mind that ship B is going at 20kph, thus from noon to 4pm, is 4 hours, so it has travelled by then 20 * 4 or 80 kilometers, thus b = 80.
whilst the ship B is moving north, the distance "a" is not really changing, and thus is a constant, that matters because the derivative of a constant is 0.