You can put this solution on YOUR website! Are you trying to say that the index of the radical symbol is 4 and the number in the radicand is 81?
In other words, find the fourth root of 81?
If that is the case, then ask yourself: What number times itself 4 times, will produce 81?
How about 3?
3 x 3 x 3 x 3 = 81
The root is 3.