To start off with, the probability to draw the short straw is 1/9 and each time someone picks the long straw the denominator (the 9) decreases by one which means that the odds of someone picking it get higher.
ANSWER

EXPLANATION
We want to find the area of the shaded region.
We find the area of the smaller circle and subtract from the area of the larger circle.
Area of smaller circle is

Area of larger circle is

The area of the shaded region is:

There were 5 of the 15 in the simulation that used a coupon. To find the probability you just divide 5 by 15
P(=>4) = 5/15 = 1/3 - probability of 4 or more