You have eaten 24% of the fiber you need.
Explanation:
From this word problem we know that we must find what percent 6 is of 25. To do this, we can set up a proportion.
    x4
6       n
---  = ---
25    100%
    x4
Our objective is n, meaning we are solving for n. As we can notice, to get from 25 to 100, we multiply by 4 (100/25=4). We must do the same thing to 6, meaning we must multiply 4 by 6. 4 x 6 = 24, therefore the answer is 24%.