Riddle:

An urn contains the numbers 1, 2, 3, ..., 2018. We randomly draw, without replacement, 4 numbers in order from the urn, which we will denote a, b, c, d. What is the probability that the following system will have a solution strictly inside (i.e., not on the axes) the first quadrant?

ax + by = ab

cx + dy = cd

Python Solution:

Riddle source: