3^9 * (7^3)^3
___________
21^7
3^9 * 7^9
________ = 3^2 * 7^2= 49*9=441
3^7 * 7^7
(3^9*〖(7^3)〗^3)/〖21〗^7 =(3^9*7^9)/〖21〗^7 =〖21〗^9/〖21〗^7 =〖21〗^2