I need help some help with the below problem and would appreciate very much if can offer some help.
A box contains 15 counters numbered 1 to 15. Counters are drawn successively from the box, one at a time with replacement. A "Win" is obtained when the first number is drawn again.
Given that the first "win' occurs on the 3rd draw, find the probability that the second "win" is obtained on or before the 7th draw.