First set up two fraction equal to each other.
You know percentages are out of 100 unless written otherwise, so you can set up your fraction with a numerator of x as the variable you want to find. [tex] \frac{x}{100} [/tex]
For your second equation because you know your numerator and your denominator you can set it up as [tex] \frac{20.57}{48.4} [/tex]
Now that you have this set up the next steps is simple math.
[tex] \frac{x}{100} [/tex] = [tex] \frac{20.57}{48.4} [/tex]
In any equation like this you have to multiply one set of opposite numerators and denominators, then use what ever number you have left over to divide what you are multiplying together
You can set up the equation (100 * 20.57)/48.4
So your final answer should be 42.5%
