Let's get the slope of this line, making a triangle between points (0, 2.5) and (15, 7.5)
tg x = oc/ac
tg x = 5/15
tg x = 1/3
So, m = 1/3
(y - yo) = 1/3.(x - xo)
Now just put a point
(y - 2.5) = 1/3.(x - 0)
y - 5/2 = 1x/3
For 40 cars:
40 - 5/2 = x/3
75/2 = x/3
112,5 = x
Making an approximation we have 115 as ans, alt B.
