The answer should be 15625x^1215625x12, if the problem is written correctly.
Explanation:
(25x^4)^3(25x4)3 is not a radical expression, but rather a simple problem involving powers.
To solve, simply apply the third power to the 25 and x^4x4, noting that when a variable is raised to one power and and then another, the powers are multiplied. Since it is (x^4)^3(x4)3, you multiply 4 by 3 to get the power 12.