# 9^3c = (3^2)^3c 27^2c = (3^3)^2c (3^2)^3c = 3^6c (3^3)^2c = 3^6c 7 x 3^6c - 4 x 3^6c 3^6c (7-4) 3^6c (3) 3^(6c+1)