a)
because it is equal to the area of the shaded region between X=4 and X=6, and the probability that X falls within some interval is given by the area under the PDF.
b)
because the shaded region is a rectangle of height 1/5 (by virtue of X following a uniform distribution over the interval [2, 7], which has length 5).
13-5=8
8+7=15 answer is 15
Intersect with x axis indicates that x value would be Zero
Thus when x = 0
y would be
y = -18
Therefor intersection would be at (0,-18)
The answer is x=K/b + 2/b.