2012 AIME II Problem 2

Two geometric sequences a_1, a_2, a_3, \ldots and b_1, b_2, b_3, \ldots have the same common ratio, with a_1 = 27, b_1=99, and a_{15}=b_{11}. Find a_9.

Leading zeroes must be inputted, so if your answer is 34, then input 034

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.