A)
y = ax + b
b = 40 as the line starts at (0 ; 40)
then the line goes down => so a < 0
between the 1st point and the second, we go 2 units on the right and we go 1 unit down
so a = - 1/2 = - 0,5
finally y = - 0,5x + 40
B)
y = ax + b
with
a = (-6 ; 0) / (0 ; -30) = 6/30 = 1/5
with the point ( 0 ; -6) we know that b = -6
finally y = 1/5x - 6
C)
we use the point (0 ; - 10)
so Amir is right as b will be - 10
