Answer: 84%
Explanation:
1. Since 25 is the output value, we can assume that it is 100%
2. Now we out what we want to find with x
3. From step one, 25=100%
4. In the same line, x%=21
5. This gives us 2 equations:
100%=25(1)
x%=21(2)
6. By dividing equation 1 by equation 2 and taking note of the fact that both the left hand side of both equations have the same unit (%); we have (set up a proportion)
7. Then, take the reciprocal and solve. You should end up with x=84%